NHF – new heroes for Heroes V 3.1.

He compiled statistics: he killed about 5000 creatures per game, which is about 200 skeletons.

Compare this to the number of Tier 1 creatures, similar to skeletons, that you have by the end of such a game. And compare it to the specialization on a unit at that level (for example, at level 20, bonuses of +10/10 are equivalent to +40% to the number of units). Because simply having 200 skeletons is just a number that doesn't mean anything.