Hi Wedado,
The maximum number of APs managed by an AC is as follows:
AC6003: 48
AC6005: 128 (versions earlier than V200R006C10); 256 (V200R006C10 and later)
AC6605: 512 (V200R003); 1024 (V200R005 and later)
ACU2: 2048
By default, the number of APs managed by an AC (without license loaded) is as follows:
AC6003: 4
AC6005: 4
AC6605: 4
ACU2: 128