This read-write value, from 0 to 240 in steps of 16, sets this port's priority for designated/blocked tie-breaking within a specific MST instance. An admin adjusts it per instance to control load distribution independently for different VLAN groups sharing the same physical ports. For example, setting port 2's priority to 0 within instance 2 only biases VLANs mapped to instance 2 toward using that port as designated, without affecting how instance 1's VLANs are forwarded.