This counts Available Seconds on this SONET/SDH port for this bin: the seconds during the interval that were not counted as unavailable, per the MIB's description. AS is essentially the complement of UAS for this bin on this port -- it's the 'good time' denominator admins use alongside Total Time to compute the actual uptime percentage for this specific interval, rather than working the number backward from the unavailable count alone; because this bin is a closed, archived 24-hour interval, admins typically read it the next day to judge whether the previous day as a whole met SLA rather than to catch a fault as it happens. For a 900-second bin, an AS value of 805 would correspond directly to 95 unavailable seconds in that same window on this port.