Board Thread:Theories and Speculation/@comment-36512555-20200101053037/@comment-4961229-20200415211822

Kirin struck at 1/1000th of a second once Sasuke's hand reached the end of its motion. That means Itachi had 1/1000th of a second added onto the time it took Sasuke to execute his hand motion to get Susanoo up or he would have died.

Total Reaction Time = Sasuke Hand Motion + 1/1000 sec

Plenty of time in top tier ninja circles.