This is a 64-bit high-capacity counter tracking the total number of receive errors on the VSL, avoiding 32-bit wraparound under sustained error conditions. An admin cares because it's the reliable long-interval version of the receive-error counter for trending purposes on a high-throughput VSL. For example, a monitoring dashboard sampling hourly would use this counter to avoid undercounting errors that a 32-bit counter might have wrapped past between samples.