YOu know the guy sees exactly what he is drawing. Its like making an outline of what is already there for him. He is just going over the lines, deciding how dark he should make them compared to what he "sees" on the page. That would explain him getting the number of windows and columns correct.

It is amazing. LIke I have posted on this before. I know a girl that if she wrote something down, like notes in a class, she could see all of her notes in her head. She could read straight off her notes.
I used to test her. I would read her a little bit on the 50th or so page of her notes, and then she would just continue reading exactly, every word on the page. She even knew the places she had erased or scratched out. And if she drew any pictures to complement the notes... When I asked her to rewrite the notes. The words would be in EXACTLY the same place on the page. Same words ending the line and beginning the next. Exactly. Same puntuation.
She SAW the notes. Not quite as impressive as this guy, but it blew me away. Sad when she had to drop out of law school. She could "see" all her notes, but once she had to analyze, predict... higher order stuff that was not directly on the page... no go.

Idiot Savant of sorts I guess. An amazing curse.