[GAMEPLAY] Mastery not giving the correct amount of AP

So I’m getting 19 AP , even though it clearly states that you get +2 AP per 1% cdr that you have too much of. So how is it possible to only get +19 ?

You can see the items , Redemption+Ardent Censer+Forbidden Idol+Kindlegem , I'm at 40% CDR + Transcendence would make it 50% , and I should only get +10 AP. But somehow I'm getting "+19?" It wouldn't even make sense since you can only get +2 PER 1% cdr.

I hope this won't get ignored.