You choose the seat pitch and how many seats abreast. The game then calculates a seat width and subsequent comfort rating with the prior information.
e.g. I choose 32" seat @ 3-3-3 on a 777-300ER. The game then calculates that seat width is 18.5" and provides a rating of 80.
Well, what configs will be available, 3-2-3, 3-3-3, 3-4-3, 4-4-4, so on.