I'm not sure you get the "math". A couple of tweaks an I can make any foe near unbeatable or an easy target. Plus adding in the environment, setting, effects and foe tactics.So if you don't fudge because you don't need to because you get what you are expecting 99% of the time. But math says that you don't actually get what you expect with near that certainty.
Example: I want the characters to fall into the trap at spot x.....so some foes attack and then run away to spot x. Like 99% of the time the crazy mad xp thirsty players will chase the fleeing monster...right into the trap. The "math" does not matter.
If I want some character death I toss in a 3d encounter...like being underwater. Many players get super frustrated with 360 attacks and it leads to easy character death.
I guess you are thinking that combat is just rolling a bunch of dice and seeing what happens? My point is that I don't do that. I don't hinge things I want in my game on such combat. I do LOVE tons and tons and tons of randomness.......but things I want happen as I create/alter the game reality.