This is a running count of all receive errors the card's AAL5 reassembly processor has detected while reassembling ATM cells back into AAL5 packets. Because AAL5 reassembly errors, like CRC or length mismatches, usually trace back to upstream cell loss or corruption rather than this card itself, a rising count here is often the first sign of a problem elsewhere on the ATM path feeding this card. A jump of several hundred errors after a carrier maintenance window would suggest the upstream ATM circuit, not this card, introduced cell loss that the AAL5 processor is now flagging.