This counter reports the IPv4 packets dropped from this queue because its total packet count exceeded the configured maximum threshold, i.e. a straightforward tail drop once the queue was full. It applies to a transmit queue on a subscriber circuit's session where QoS queuing is enabled. Admins track it per queue to see how traffic is actually being scheduled and, for the dropped variants, where congestion is forcing discards on this subscriber circuit. Discontinuities in the value can occur when the management system re-initializes, so a sudden reset does not necessarily mean the underlying activity stopped.