So, I played Arena just few minutes ago.
Palyed Cho'Gath.
Picked up an augment that converts your bonus AD to AP and gives you 15% AP called ADAPt.
I know that Cho'Gath has pretty high base AD.
I decided to buy Sterak's Gage.
I had like 130 AP after that.
Then I decided maybe I don;t want to have it so i clicked "Undo".
Then I was thinkig what do I really want, decided to buy Sterak's Gage anyways.
Suddenly I had like 124 AP.
Did the same thing again 123 AP.
Again had like 101 AP.
(I always waited for a bit just to be sure it is a stable value)


So I just ended up with another item instead.