Every time Poe would play with his tailfeathers, those same tailfeathers would flick about. He was fascinated by just how complex numbers could get.

He listened, enraptured. He tried to understand things on the first try, frowning in thought.

During one pause when Poe was clearly going to backtrack, Scrooge asked about something that had been read earlier, relating it back to the present topic. The topics seemed similar...but he likely was wrong.