This counter reports the number of Errored Seconds encountered at the Section layer during one specific historical 15-minute interval within the past 24 hours, indexed by cwSonetSectionIntervalNumber. An admin cares because walking through this table across all 96 intervals lets them build a timeline of exactly when section-layer errors occurred over the past day, rather than only seeing the live current-interval count. For example, finding a spike in this counter at interval 40 while intervals around it are near zero pinpoints a specific ten-hour-old event rather than an ongoing chronic problem.