I think it's worth it to expand a little on the quest mechanics now that Finn has (2/10) in both an Attribute (Body) and Skill (Green Arts).
Say Finn is outside and has to pull a Mandrake out of the ground for whatever reason.
First, there would be a D100 roll competing against a DC. In order to not make things based purely on chance, I would then add the relevant Attribute * the relevant Skill to the roll result.
So let's pretend he rolled a 50. For this specific scenario, I would then add the result of Finn's Body Attribute (2) * his Skill in the Green Arts (2) for a +4 modifier. Making the end result 54.
The general idea being that if he topped out (10/10) in both the relevant Attribute and the relevant Skill, he would never get anything less than a critical success no matter the D100 roll (the modifier would be +100). Or to put it another way, he is so good that luck (the D100 roll) has nothing to do with it.
On the other hand, if he was absolute trash in both the Attribute and Skill (1/10), his success would depend on almost nothing but luck (+1 modifier).
Hope that makes sense. Although to be clear, don't expect to get (10/10) in anything really. That's Dumbledore level, nothing that a student should be able to reach.