Okay, the memcalc is clear on how to modify the max number of hp on a unit. I can't seem to be able to figure out how to change the health of a unit within its max health (ie changing a hatchery from 1250/1250 to 625/1250). For the triggers I am working on, modifying the percentage with ordinary triggers won't do the trick. I believe the secret is using the EUDs, but they don't seem to cover this aspect.