I have the CG3000DCR with a /56 assignment and a Cisco ASA (5506-X) attached. I do have ::/56 configured as my PD hint but I am only receiving a /60. I opened a ticket with the business support group to check the DHCP reservation on their side but was told they don't reserve addresses and have never heard of this issue happening before.
Thanks so much for reaching out, MagellanTX. I'd like to see if we can figure out what's going on with this. Can you please click on my handle (Comcast_Gina) and send a private message with your name, the business name, the complete service address (including city, state, ZIP, suite number, etc), and the phone or account number?