This counter tracks Severely Errored Framing Seconds — seconds during which the Section layer's framing pattern itself was so disrupted that frame synchronization was lost — accumulated during the current 15-minute interval. An admin cares because SEFS specifically indicates loss of frame alignment, a more fundamental problem than bit errors within an otherwise-synchronized frame, and typically correlates with a complete or near-complete outage on this span during those seconds. For example, a burst of SEFS counts alongside a Loss of Frame defect flag in cwSonetSectionCurrentStatus confirms the section actually lost sync, not just accumulated bit errors.