This counts seconds during which this E1 port was in the formally unavailable state, entered after ten consecutive severely errored seconds. UAS is the number that belongs in an SLA or outage report for this specific E1 port, since it reflects actual counted downtime rather than degraded-but-still-passing-traffic seconds -- 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 60 -- a concrete count the admin can trend against neighboring bins to judge whether the condition it reflects is worsening.