How is a "Modifier Magnitude Calculation" working for Ability Costs?

ok… interesting funfact… since… it´s still not working… or… working but not really… damnit…

I updated the Definition and added a GEngine print to Screen, with the current Cost, the regeneration of the Attribute and the Outcome after calculation…

I duplicated the Class 3 Times, one for each Cost attribute in order: Stamina, health, mana, Arcanum

I also set the Costs (in the the order mentioned):
25, 10, 20, 30

Problem 1:
The AttributeCost print… is always 0… no matter what costs are set… BUT… and that´s the interesting part… the Attribute gets reduced BY that cost… Except for Stamina… stamina is not working… Even its the same functionality and SetByCaller as the other Attributes…

Here is how i set all:

And here is what it looks in Game:
2
(Arcanum start at 0… but its working on a previous test…)

Questions now:
Why are the Prints of GEngine all 0… But the value gets subtracted from the Attributes?
Why is stamina still not doing anything… Even it´s the same calculation as the other Atts?