This read-only Gauge reports the number of Errored Seconds encountered by this DS1 interface in one specific historical 15-minute interval (identified by dsx1IntervalNumber), the completed-interval counterpart to the still-accumulating dsx1CurrentESs. This lets an admin look back at exactly how many errored seconds occurred in a particular past 15-minute window rather than only seeing the live, in-progress count. An engineer correlating a customer-reported outage time against the switch's own records would find the matching dsx1IntervalNumber for that time window and check dsx1IntervalESs to confirm the switch also observed elevated errors then.