This counts Synthetic Loss Replies this device has sent in response to SLM test frames received from a remote MEP running a synthetic-loss test toward this device. Since this device's role here is purely as a responder echoing test frames back so the initiator can compute its own loss ratio, a mismatch between SLMs received and SLRs sent, tracked separately in the responder table, would mean this device itself is the source of measured loss in someone else's synthetic-loss test, worth ruling out before blaming the network path.