2015 stats per TEA/AECOM:
Typhoon: 2,294,000
Blizzard: 2,107,000
Aquatica: 1,600,000
Wet n Wild: 1,310,000
That comes out a daily average of...(ignoring their seasonal closures)
Typhoon: 6,284
Blizzard: 5,772
Aquatica: 4,383
Wet n Wild: 3,589
So i'd say at minimum they want 3,500 people there per day, on the high end they'd like 6,000+. The two parks it's attached to have 26-24k guests each day. Say like half those people are shared park hopper and the actual "bodies boppin about" is like 36k then they want at minimum to snag like 10% of those people, 15-20% and they're rolling in the dough.