The Ides of March : Mistake at 1:11:15? (Hand appearing from the off)

At 1:11:15 Stephen and Tom are supposed to be alone in a room when all of a sudden a hand in a black glove reaches out from the off touching Stephen's/Goslin's shoulder for a blink of an eye who seems very briefly irritated and then continuous with his text. Anybody else resized that? It happens when Stephen says "This is[hand comes in].it's my life you are talking about". That is a mistake, right?

It looks like Stephen waving his hand. He is either wearing or holding the gloves he came in with.

@BethyMadeira I think it's a goof, too. They're alone in the room, and yet Stephen was looking at someone else.

It's not a goof, he has gloves in his left hand and waves his hand up and to the left.

Definitely a goof, it gave me a fright the first time I saw it. Just watched it again. It can't be Stephen's own hand, or Paul's, the angle is wrong. I'm not sure why it was. Great scene though.