Exactly as described, this counts received packets on this benchmark port that failed a length-check validation, where the frame's declared length field didn't match its actual size. This specifically implicates the Length/Type field encoding of received frames rather than payload corruption, which can surface when interoperating with a non-Ciena third-party test generator that encodes frame headers slightly differently than expected. For example, length-check errors appearing only when testing against a particular vendor's traffic generator, and never against another, would point to a header-encoding incompatibility with that specific vendor's equipment.