This read-only Counter64 is the count of bytes currently pending (queued but not yet sent) for this QoS Class. An admin watches this to detect queuing buildup for a specific traffic class, which is an early warning that this class is being starved of bandwidth on the VPath. For example, a growing bytes-pending count on the interactive class while the bulk class's counter stays low suggests interactive traffic is being queued behind other traffic and may soon experience latency.