This counter tracks frames that were NOT transmitted because they hit the maximum configured number of collisions, and the MIB explicitly notes it should only increment when the network is heavily saturated with traffic. Because the description itself flags heavy saturation as the expected cause, this counter incrementing on a link that isn't under heavy load points instead to a duplex mismatch or a faulty cable/switch port rather than genuine congestion. If this counter starts climbing on a link running at only a small fraction of its capacity, an admin would suspect a half/full-duplex mismatch with the attached switch port rather than actual traffic saturation.