This read-only counter tallies reassembled frames intended for transmission on this connection where the AAL5 PDU trailer's declared length didn't match the actual reassembled length, and were discarded. This specifically catches corruption where cells were lost or duplicated in a pattern a length check catches but a simple cell count wouldn't, distinguishing it from the CRC-error case, which catches corruption within an otherwise correctly sized frame. A single lost cell in the middle of a multi-cell AAL5 frame would often surface here as a length mismatch, since the reassembled data would be short by that cell's payload.