Here is the full message:
"as for the eye crit modifier from helmets, I -believe- it is a negative mod to the crit modifier that armor provides. So if you crit and roll damage is 50, armor crit mod might be(this is example, not sure how formula works) is 40, taking 40 damage, I imagine the perk lowers that even more by -25%.
That is a bad formula example but I hope it kinda gets the point across. It doesnt effect the critical roll hit, I think. Just crit damage."