This read-create Unsigned32 (0-16) sets the length in bits of the Port-set ID configured for this rule, corresponding to the MAP-DHCP S46_PORTPARAMS PSID-len field, now applied per rule rather than per tunnel. An admin adjusts this to size how many distinct port-sets, and thus how many co-sharing subscribers, the mapped IPv4 address supports. For example, a PSIDLength of 6 combined with the offset determines exactly how many high-order bits of the port number the gateway uses to distinguish this subscriber's port-set from others sharing the address.