This PerfCounter64 counter reports the lowest instantaneous receive bit rate seen in any single 1-second sample during the interval. An admin compares it against the access port's provisioned capacity to see whether traffic is running near, over, or well under what the port or flow is supposed to carry. If cmEthernetAccPortHistoryIBRMinRx on access port 42 settles around 824 Mbps at the most recent completed bin, an operator sizing that port for an upgrade has a concrete number to compare against its provisioned limit, rather than guessing from aggregate port utilization.