Well, the sequence goes like this:
You commit X XP, then spend Y (where Y<X) XP on training someone. Z equals (all Y combined). You can also end the charm at each time, regaining any X but keeping your pool of Z.
At the end of each story, you roll Z. All successes (Zsux) from that roll give you XP (ZXP, but your XP gained from this may never be larger than Z.
You may use Solar Experience for X (and therefore Y), but your regain from Z is in normal XP.
If you have Tireless Learner Method, you also gain an additional option:
Each time you roll Z, you may spend 1 XP. That XP is NOT added to Z - but now, you keep all experience granted by the roll, even if ZXP>Z.
Example:
You commit 10 solarXP. You then teach some peasant (or a Circlemate) Medicine 3, costing you 9 out of those 10 solarXP and raising your "spent pool" to 9. You can now end Flowing Mind Prana, giving you 1 solarXP back.
With Legendary Scholars Curiculum and Essence 2, you could instead teach a large class. Two of that would become full-blown doctors (Medicine 3), while the other ten could still learn Medicine 1. Or you spend the full 10 XP, still granting the two doctors Medicine 3, but the others Medicine 2 (costing 5 XP, half of those 10 XP). This does not alter your "spent pool" in any way though.
After you're done with teaching the Medicine, you teach them some Bureaucracy. You only commit 6 solarXP - enough to bring two of them up to Bureaucracy 2, and the other ten to Bureaucracy 1. Since you spent 6 solarXP, this brings your entire "spent pool" to 16.
Now the story ends. You roll 16 dice, and get 8 successes. Thus, you gain 8 XP.
Now, let's end another story. You still roll 16 dice, but this time you get 10 successes - however, you only get 8 XP since you're limited by your "spent pool".
If another story ends now, you'd still get to roll 16 dice, but could not possibly gain any XP from it (since you're already at cap). If you however spend another 10 XP to teach someone, this brings your pool up to 26. You'd roll 26 dice, but get at most 10 more XP.
Now you learn Tireless Learner Method. Another story ends. You spend 1 XP to activate the charm, and roll the 26 dice. You get to re-roll all non-successes too, so lets say you get 20 successes. This means you get 20 XP (!!), though they will likely not contribute to raising your Essence.
Yeah, this gets insane pretty fast. Especially since nothing prevents you from using the XP you get back from the charm to activate the charm again.
If we assume an average of 4 sessions to the story, this is what a Twilight Loremasters XP-progression could look like:
Supernal Lore, Lore 5, and 5 charm purchases on the Teaching-charms. Allowing them to teach Solar Charms to other solars.
In the first two sessions, they get 8 solarXP. That is promptly spent on teaching a circlemate one charm. In the next two, they gain that much SolarXP again and spend them on teaching a circlemate another charm. The story ends, and they roll 16 dice, gaining 8 XP which they can spend on a Solar charm.
Over the next four sessions, the pool is brought up to 32 and they potentially taught another two charms to circlemates just from their own solarXP. Rolling normally would give them 16 XP, or in other words to Solar Charms.
They are now at 64 XP - enough for Essence 2, while their circlemates are still at 40 XP.
We go with another four sessions, and another two charms taught, and now a pool of (24/48). Rolling normally would give 24 XP - but they instead decide to activate Tireles Learner Method. So they gain 36 successes and thus 36 XP (-1 for the activation) - enough for four solar charms. Instead
Their pool is now at (60/48), with their XP are at 108. Their circlemates have caught up to Essence 2.
Another four sessions, same thing. Pool is at (60/64). Story ends, TLM, they get 48 XP - enough for six solar charms. Their XP is at 144, they're Essence 3 now while their Circlemates are still at 80 and thus Essence 2.
Again, with pool (145/80). Gain 60 XP. Their XP is at 180, circlemates at 100 (not even Essence 3 yet).
Again, with pool (205/96). Gain 72 XP. Their XP is at 216 - Essence 4, circlemates are still Essence 2 with 120 xp!
So yes, that's some pretty insane stuff. Buut we haven't even gone recursive yet! What if all the regained XP is spent on teaching again and use TLM sooner??
All earned SolarXP goes to teaching (so 16 XP/4 sessions). All re-gained XP goes to teaching too. Use own SolarXP to learn charms to teach to circlemates.
Session 4: Pool is (8/24) because we re-invested those 8 XP into teaching.
Session 8: Pool is (38/70). Roll 40 with TLM, gain 30 XP. Reinvest that into teaching, bring the pool to 70
Session 12: Pool is (102/150). Roll 86 with TLM, gain 64 XP. Reinvest, pool is at 150
Session 16: Pool is at (228/290). Roll 168 with TLM, gain 126 XP. Reinvest, pool is at 290.
Session 20: Pool is at (456/534). Roll 306 with TLM, gain 228 XP. Reinvest, pool is at 534.
Session 24: Pool is at (868/912). Roll 550 with TLM, gain 412 XP. Reinvest, pool is at 912.
Session 28: Pool is at (1837/1624). Roll 928 with TLM, gain 696 XP. Reinvest, pool is at 1624.
Yeah, that's...., here, you reach Essence 2 after 5 sessions, Essence 3 after 10 sessions, Essence 4 after 12 sessions, and Essence 5 before 16 sessions are over. While the normal progression is Essence 2 (10 sessions), Essence 3 (25 sessions), Essence 4 (40 sessions) and Essence 5 (60 sessions). You're essence 5 before your circlemates are even Essence 3. Granted, you could also theoretically teach them every single charm you yourself know, to all of them - looking at your pool by Session 28, you taught them 1624 XP worth of charms, abilities or attributes. I kinda doubt whether you could even possibly have that much to teach.
At this point, if you stop reiterating and just reap the XP you gain for yourself - well, a single story will now grant you 1254 XP. That's more than your Circlemates have earned in their entire lifetime (228), together (1152). That's enough to learn any non-favored ability at 5 (31 XP) and learn all it's charms (30 charms at 10 XP each =300 XP) - three times. You'll have mastered every ability, learned all its charms, raised all your attributes to 5, bought all merits, mastered all martial arts and learned all spells quite shortly, I suspect.
So yeah, either this is badly designed or people are misreading the charm (in which case it is badly written).
