This counter tallies Ethernet frames sized exactly 64 bytes (counting FCS octets, excluding framing bits) that were received with errors across all ports in a group, the errored counterpart of the matching Ok-sized bin. A nonzero and growing value in this specific 64-byte error bin points to a physical-layer problem affecting frames of roughly that size on the group's shared wiring. An admin comparing this counter against gsobkt64Ok on group 1 could estimate what fraction of 64-byte traffic on that microhub is arriving damaged.