Agree, mathetmatically it doesn't add up. They should implement a penalty escrow. So team A commits a personal foul at the 5 yard line, they move back 2.5 yards to the two and a half yard line. Then next time they get the ball, those 12.5 yards that weren't assessed can be distributed. It would be easy to track and implement. That way all fouls are worth the same amount of yards.