For subscriber traffic monitoring and for gather data consumption, which you inputOctet & outOctect, you require to setup AAA server for accounting.
The mib in dynamic-profile does not help becuase you dont want to poll mib every time to monitor subscribers and doing so will burnet load in SNMP processs. JUNOS Telemetry isn't fully quailied for subscriber mgmt accouting use.
We have about 150+ ISP using juniper MX as subscriber-mgmt node, the best parctise for accounting data traffic is to setup accounting server. A free radius as your authenthication server can aslo be setup as accouting server.