I saw lots of empty seats in all the stands, except below me in SS 1&2 that I couldn't see. No way was there over 53k there. The club probably count those who have a SC whether they are in attendance or not.
Fair enough if people can't make the game for personal reasons, but if I can't make a game, I phone the club and get them to email me an e-ticket for my seat which I then forward to a friend so my seat is not unused. I hate my seat going to waste when a friend will gladly use it. If others could be bothered doing this, then there'd be less empty seats throughout the stadium.