This PerfCounter64 counter reports the maximum post-rate-limiting bits-received value in any single 1-second sample on the network-side port during the interval (measured after the flow's rate limiter, so it reflects the shaped, delivered rate rather than raw demand). An admin compares it against the subscriber flow's provisioned capacity to see whether traffic is running near, over, or well under what the port or flow is supposed to carry. If cmFlowHistoryIBRRlN2AMax on flow 38 settles around 129 Mbps at the most recent completed bin, an operator sizing that flow for an upgrade has a concrete number to compare against its provisioned limit, rather than guessing from aggregate port utilization.