This value counts, in seconds, the intervals where the OTUC2 signal's error rate crossed the severely-errored-second threshold, a stricter tier than ordinary errored seconds. Operators rely on this metric to catch bursts of heavy corruption on a 200G channel that a plain errored-seconds count might understate. A jump in severely errored seconds right after a card reseat, for instance, would tell a technician the reseat itself briefly disrupted the OTUC2 signal.