This PerfCounter64 counter reports a count of bytes transmitted on the flow, in the downstream (network-to-subscriber) direction in the downstream (network-to-subscriber) direction, tallied over the current interval. An admin uses it for precise usage accounting on one specific subscriber flow, separate from the aggregate totals on the physical port it rides. If cmFlowStatsBytesOutN2A on flow entry 25 totals roughly 80 MB for the interval while the flow's rate-limited counterpart is far lower, an operator can tell how much of that subscriber's offered traffic is actually being shaped away rather than delivered.