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 closed 24-hour history bin -- a final, day-over-day comparable count rather than a live figure. For example, over that completed 24-hour bin, 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.