Adaptive bonus after max cdr for ad slightly lower

Basically I was looking at my masteries in game and it said for each % cdr you get 1.2ad or 2ap adaptive, I was playing kayn and going ad, had 10% cdr over the limit and it said it was giving me 11ad not 12 ad so just a tiny bug there. 1.2 x 10 = 12ad not 11 ad.