This counter tracks the number of RS (Resynchronization) PDUs received on this port, per the description, meaning the far end detected a sequence-number inconsistency and is asking to realign SSCOP state without a full link teardown. A rising count here that isn't matched by NumRsPduTx suggests the desynchronization is being detected primarily from the far end's perspective, which can point at a receive-side sequencing issue specific to how this port is processing inbound sequenced-data PDUs. This is a moderate-severity signal worth trending rather than an emergency on its own.