There's only 4 business and 10 economy difference between the B762/B752 with US. Is the service at 100% capacity already? If that's the case, that's pretty impressive for a service in it's first month and before the school holidays.
Apparently 1 spare seat inbound and 14 outbound today. They made the effort to fit everyone on by swapping CLT-BRU to the B757 and CLT-MAN the B767. Also apparently very little slack in the other 3 flights for overbooking.
Maybe it goes to show that for at least summer, 4 daily AA isn't quite as crazy as first thought?