Use the time line to scrub the video and put your eyes on the ring finger of the left hand. The pinky dissolves into the hand, and the ring finger "becomes" the pinky.

Now put your eyes on the index finger of the left hand and track it visually. It "becomes" the middle finger, and an entirely new finger appears to take its place.

That what I thought at first. But additional finger pops up and he still have 5 even with index finger hidden.