This counter tallies Ethernet frames sized between 512 and 1023 bytes (counting FCS octets, excluding framing bits) received on this one port with errors, the per-port breakdown of that size bin's error count. A single port, such as port 1, showing a disproportionate share of this error bin compared to its neighbors in the same group points at a cable or connector problem specific to that jack. An admin narrowing down a group-wide 512-1023-byte error spike would check each port's version of this counter to find the one physical connection responsible.