This counter records the number of bytes dropped from the tail of this access port's shaper queue because it was full. A rising value tells an admin the access port's shaping buffer is overflowing, meaning the subscriber's offered traffic exceeds what the port's shaping rate allows, causing loss. For example, if a subscriber complains about stuttering video and cmAccPortQosShaperStatsBTD is climbing, the admin would consider raising that access port's shaper rate or buffer depth.