Exactly as described, this counts packets received on this benchmark port longer than 1518 octets that were otherwise well-formed. During a jumbo-frame test using a generator H frame size above 1518, this counter incrementing is expected and healthy; seeing it increment during a test that should only be using standard frames instead flags an unintended jumbo frame leaking onto the path. For example, a test profile configured for a fixed 9000-byte jumbo frame will naturally drive this counter up in lockstep with received test packets, which is normal for that specific test.