During half time when colt handled the balls they found it to be a lot lighter than its usual weight, which is 12.5-13.5. Also, the ball pressure does matter because it increases it's distance height and grip and most football plays would say a deflated ball has a lot better brio than a regular ball.

How they found out was,during the game the colts handed the footballs to the quarterback Tom Brady and he said that they felt more lighter than they usually are. So the refs weighed them and they weren't up to the standards.