This counter reports, in bytes, how much of this card's frame memory is currently occupied by frames sitting in its Hold Queues rather than already transmitted. A Hold Queue backlog on this card means downstream frames are being queued rather than forwarded promptly, so watching this value rise over time flags egress congestion specific to this card's outbound ports. If this value climbs steadily toward the card's total frame memory capacity, say 4 MB, it signals the card is close to exhausting queue space and will soon start discarding frames.