Per its DESCRIPTION, this Counter64 counts seconds declared unavailable based on the P-bit performance parameter rather than the line-side counters. Because this row is one of the already-completed short intervals rather than the one still filling, a reading here means the DS3 circuit was declared unavailable specifically per the P-bit (far-end) measurement, not the line counters on this DS3 circuit, within that one specific closed interval, which you can pin to an exact clock window using this row's StartTime and EndTime. For example, a reading of 0 seconds in this bin on this DS3 circuit even while the line-side Uas equivalent stays at zero tells you the far end declared an outage that the near end circuitry did not itself detect.