This is a 64-bit high-capacity counter tracking the total number of received VSL packets with checksum errors, avoiding 32-bit wraparound on a busy link. An admin cares because it's the dependable long-term counter for spotting a trend of physical-layer corruption on the receive side of a high-throughput VSL. For example, a gradual upward trend in this counter over several weeks, tracked reliably without wraparound, would be a strong signal to schedule replacement of the VSL's physical transceivers or cabling.