This counts the seconds in which this E1 port had at least one errored block. As the seconds-based counterpart to EB, ES on this port tells the admin how much of the elapsed time was affected by any error at all, the number typically compared against a G.826-style error-second-ratio threshold for the circuit -- and this specific object covers a cumulative counter reset only by an explicit clear rather than on a fixed schedule -- reflecting everything since PM stats were last cleared. For example, since PM counters were last cleared, this E1 port might show this counter at 300 -- a concrete count the admin can trend against neighboring bins to judge whether the condition it reflects is worsening.