Yes, you want the AA Lines set to 4 rings and CFNA on all ringing phones set to 6 (there is no 5 ring setting on the phone, it goes from 4 to 6 to 10. This way the incoming call will get answered by the AA after 4 rings before the number CFNA rings on the phones is reached.
You can try setting both to 4 rings, but do a lot of testing to make sure the AA that you want answers reliably every time.