Pretty sure I read this on a private BB USA forum
You can only buy 50 luxury boxes and 500 courtside seats. So you eventually want to max those out.
Assuming the soft cap of 20K, you want to divide your Bleachers/Lower Tier into something that adds up to 20K. It's easier to sell bleachers in lower divisions. Easier to sell Lower Tier in higher divisions.
I'm not exactly sure how it all plays out. Looks like you sell out your LT and have empty bleachers. It's not explained at all in the manual. But you can page through a lot of teams and attendance always seems to top out in the 20000s.