If by numbers over heads you mean over the monsters before you fight, the 1,2,3,4 that appear before you actually get into the frenzy of combat, is which character has selected an action on what monster.

If your talking about hits purely, then more hits means more damage, and you get more hits as your levels increase (both normal level and job level I believe). I don't know the specific calculations if that's what your asking, but I'm sure it's out there somewhere.