The PRI prompt in the D-Channel configuration tells the system how to number the B-Channels across the multiple spans.
The PRI with the Primary D-Channel is alway number 0, the PRI with the Backup D-Channel is always number 1, then you need to continue with 2 being the 3rd PRI in the group, 3 being the 4th etc.
I don't have my books handy, but if you already have this configuration, print out one of your primary D-Channels, and look at what is given for it's PRI prompt. You should see a list of the Loop Numbers next to the 0, 1, 2, etc (member number) of the PRI group.