[AT&T Fiber] PACE 5268 DHCP Question

Hi I am running the Asus AC5300 behind the pace 5268AC. My question: Is it possible to change the "First DHCP Address" and the "Last DHCP Address" on the pace 5268? I would like to use the "OpenDNS" servers" in these empty spaces, I am mentioning LAN page of the gateway there is the DHCP tab and "First DHCP Address" and the "Last DHCP Address" are currently. Thank you