Phone System - How does the Auto Attendant work?

We have a Norstar phone system with a Call Pilot 150. The receptionist extension has a max of 8 ports, so there can be up to 8 calls in queue before calls start getting directed to the General Delivery mailbox. I set up the auto attendant to play a recorded message, then transfer the call to the receptionist's extension. When we turn the auto attendant on, it will only allow 1 call in queue before it starts directing calls to the General Delivery mailbox. Is there a way to set the auto attendant to use all the ports before calls get directed to the General Deliver mailbox?