Antenki

Something witaj cooldown work wrong. I will try explain this (my english is not the best- sorry). I bought winter helmet and shoes with cooldown bonus (look on picture). This items gives me 30,3% cooldown ( check picture). But problem is on last picture. Dragon eye without bonus - 30sec cooldown. With my bonus 30,3% should be 21sec ( 30x0.70=21). Why i have only 23sec??? I tryed understand it i think bonus set 6.9% is not accepted.