Hello, friend!
1. The WAN priority can be mapped from the DSCP value.

2.The mapping between DSCP values and priorities

Therefore, if you use the DSCP to the Pbit function of the ONT, the relationship between the DSCP and priority can be configured randomly.
If the DSCP-to-pbit function of the ONT is not used, the ONT transparently transmits the DSCP value to the upstream device. Then, the upstream device needs to consider the DSCP value.
The value -1 indicates that the priority of data packets is not marked.
Generally, a larger DSCP value indicates a higher priority.
Marks priorities of data packets matching traffic classification rule so that the DSL home gateway can identify the packets during a traffic control.
Thanks!