This is a write-only action object: setting it to clear(1) resets every one of the per-service CFM statistics counters above back to zero for that one specific service, while reading it back always returns none(0) since it is not persistent state, per the description. This is the mechanism an admin uses to get a clean baseline right after fixing a problem on one service, for example after replacing a faulty transceiver that was causing malformed LBMs on service 5, so the next monitoring interval shows a true zero-error picture instead of carrying forward the pre-fix error counts. Because it is scoped per service via the table index, clearing it only zeroes that one service's counters, leaving every other service's historical stats on the chassis untouched.