This read-only counter reports the number of Severely Errored Framing Seconds recorded on the interface during one completed 15-minute (or daily) PM interval. SEFS specifically counts seconds where the framing or synchronization pattern was lost or severely degraded, which points admins toward framer or clock-recovery issues rather than generic bit errors. A rising SEFS count alongside stable coding-violation counts suggests a framing or timing problem on the transponder rather than pure optical signal degradation.