It's not just the master - the limit also depends on the models of the other APs and whether the master is the gateway. If any AP is wave 1, the limit is 25. If all APs to be wave 2 and the master is not in gateway mode, the limit is 50. If the master is in gateway mode, the limit with all wave 2 APs remains 25. With 200.8, the limit was increased to 128 APs if the master is not in gateway mode, and 50 if it is.