What we’re capturing there is the Damage attribute value that is being passed in from the source gameplay effect (which is the value that comes out of the damage curve table). Anything that lives “inside the gameplay effect” is captured from the source, not the target, and then you apply the results to the target. The use of the Damage property instead of health is not 100% required, but makes the math a bit easier, we found that when designers had to think of damage as “-health” it confused them and they had a hard time keeping track of the formulas
Also, posting here to point to the fact that we’re doing a live stream Thursday