from Wikipedia about Silver Spurs Arena
8,000 (Hockey)
3,670 (Theatre)
6,570 (Half-house concert)
8,253-11,403 (arena concert)
My guess is that it will be the concert configuration, and that it will be maximum capacity minus the area taken up by the media. So, about 11,000, with probably thousands more outside, and 16 to 20,000 watching online.
I believe hillary will be at the same arena next week.
I love the Rodeos held there.