There are a few posts speculating at the attendance for this show. I mentioned that I could see a few thousand empty seats in an earlier post. But, there is a more concrete estimate, as both Guy's and Richard's blogs both quote 11,000 as the attendance number. MSG holds about 19,750 max for a concert, including the seats behind the stage. I've never seen a capacity number quoted for concert seating excluding the seats behind the stage, but a guess would be about 15,000.