This field reports the number of length check error packets transmitted on the interface, exposed here as cienaCesPmExtendedTxRxAllTimeBinTxLCheckErrorPkts. 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 'all-time' counter for the extended Tx/Rx PM group has no fixed rollover schedule of its own — it just keeps accumulating from whenever the PM instance was last cleared, so a single reading only tells you the running total, not a rate. For example, a healthy port would sit at 0 for length-check-error frames in this bin; even 31 is enough to warrant a look, since this class of counter isn't supposed to move under normal operation.