Okay, people. Clothes (in this case a jacket) do not represent the bone structure. They do not entirely conform to the shape of the body.

His jacket (outlined in blue) is going a different direction that his arm (traced in red). When you wear a loose sleeve and you raise your hand, the sleeve will flare out. His arm might be going straight up, but his sleeve flared out and rested to one side. This shouldn't be hard to figure out.