How to put it in a way a necromancer would understand?
Say you have 5 skeletons. A 20% boost to your skeletons you give you one more skeleton, giving you a total of 6. A reinforcement of 2 skeletons would give you a total of 7.
Say you have 10 ghouls. A 20% boost to your ghouls would give you 2 more ghouls, giving you a total of 12. A reinforcement of 2 ghouls would also give you a total of 12.
Basic math, ain't it grand. Less digging around graves and more book learnings foul sorcerer.