How did i use the incantation so fast?

If you see the time between me casting beastial vitality and flame give me strength is slightly faster. it happens 1 out of a 1000 times to me and I have no idea how. Can't find on Google or reddit if there is some kind of timing(comparable to parrying) that makes this happen. I also wonder if it's even noticeable in this video. also the fact probably nobody will ever read this😆