This read-only Counter64 reports the transmit byte rate for this PM instance, sampled per second. Admins compare this to the port's provisioned egress bandwidth in real time to see whether a service is currently saturating its allocation, well before a daily or 24-hour total would reveal it; because it is drawn from the grand-total statistics bin for this PM instance, it aggregates across the whole PM instance rather than any single rotating window, so it's the number to cite for a service's overall lifetime performance rather than its behavior in one interval. On a 10 Gbps aggregation trunk carrying multiple EVCs, a live reading of 3,186,117,604 bytes/sec against a 10,000,000,000-bps port tells an admin roughly how close to full the link is running right now.