I don't think it works by division. But afaik based on the post in the forums, it seems to be around 21k regardless of country and league. I've seen people selling 22k to 24k seats tho (can check my league, there are teams who overbuilt their arenas), but your ticket price has to be so low that it's not worth it. The sweet spot should be around 21k, something along the lines of approximately 15k bleachers and 5k lower tier. I've got 6k lower tiers myself, but some times I wonder if it is really worth it.