If he has three seperate monitors each of them will have a case of some sort sticking out so from the left end of the middle monitor to the right end of the left monitor there would be a certain distance between the pixels (20-50mm I guess). He just compensated that effect I think.
Well the jokes on you! They're lined up pretty well when you take the bezels into account. I actually do have the full panoramic shot that isn't cut up into 3 pieces like that also. I took it last year Friday morning at Grand Am practice, I love being one of the first people at the track for actual practice.