We only get the Calculation Hearts we need and no more, no reason to get anymore
You're allowed to assign
as many spare Calculation Hearts as you have to an extra Action, with roll 1d100+5*numCalcHeartsAfterTheFirst. This must be a Learning or Stewardship Action, or one of a few odd Actions such as Planetary Acquisition.
Normally, I'd say "grab an extra one for an extra +1d100" and call it good. However, if you bulk-order Calculation Hearts, you can get them quite cheaply. And, as it so happens, we don't have a good way to rapidly-complete large Stewardship Actions.
For example, let's say Atraxus wants to complete Foundational Medical Care. Working on it directly, at 1 Action/turn, he'll take an average of 2100/255=8-9 turns. If he chose to try to complete it in one turn, he would need (2100-53)/202=10-11 Actions. Either of those is a very expensive option, given just how much Atraxas can do with 8-11 Actions.
By contrast, if we bought 200 Calculation Hearts, we could put them on the job and they'd finish in 2 turns (and
maybe a single Urma Action).
Given that Planetary Acquisition is a massive (500 DC) Action that we're going to need to run maybe 50 times, well. I feel safe in saying that this investment will pay off (barring a saboteur managing to destroy them all or something).
It's roughly equivalent to "+5 Atraxas Actions per turn, but they must all go into a single Stewardship category."