This counts seconds in which this E1 port's error rate crossed the severe threshold -- a high proportion of errored blocks in that second, or a defect such as loss of frame. SES on this port is the counter unavailability is derived from (ten consecutive SES roll into UAS), so a sudden SES burst here is the leading indicator that this E1 link is about to be counted as formally unavailable -- and this specific object covers the current, still-open 24-hour interval -- the earliest daily-scale warning available before the full day's history bin closes. For example, so far in the current, still-running 24-hour interval, this E1 port might show this counter at 30 -- a concrete count the admin can trend against neighboring bins to judge whether the condition it reflects is worsening.