This field reports the number of length check error packets transmitted on the interface, exposed here as cienaCesPmExtendedTxRxStatsBinTxLCheckErrorPkts. On this Ciena CES port's PM data, this fires when the 802.3 length/type field didn't match the actual size of the frame before it left this port, i.e. a malformed frame was assembled internally rather than corrupted in transit; and this sits in the currently active extended Tx/Rx interval bin — its sibling StartTime/ClearTime fields mark exactly which window is being counted, so a change here reflects activity happening in the live collection interval, not something already filed away in history. For example, a healthy port would sit at 0 for length-check-error frames in this bin; even 0 is enough to warrant a look, since this class of counter isn't supposed to move under normal operation.