This Gauge counts the number of RFI (Remote Failure Indication) failures reported by the far end during the current 15-minute interval. An admin cares because RFI is the far end's way of telling this device it detected a failure looking back this direction, so a rising count here means the remote side is actively signaling trouble with what it's receiving from this device. For example, a Far-End FC count increasing at the same time local transmit power readings drop would tie the far end's RFI reports directly to a degrading local transmitter.