Ring Group goes to voicemail prior to ringing all extensions in HUNT group

Hi:

We have a hunt group for Team Support that rings all our extensions, and all our cell phones for 10 seconds each. If there is no answer, it should go to our general delivery mailbox, however, it gets to the last phone, rings once, then goes to voicemail. Is there another way this should be setup? How does it no when its time to send to voicemail if there are 30 people in the HUNT?

Thanks!