For that specific Sunday matinee, I was there a little before 11:30 and the box office opened at 12:30 (an hour before the first matinee, which was 1:30 for Head of Passes for that day). I think the second person arrived around 11:45. There just happened to be quite a few rush tickets for Dry Powder on that day. Not sure if that'd be the case for all the remaining performances. That said, Head Of Passes didn't have any rush tickets available.