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 an archived, completed daily bin, 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, for that one specific archived calendar day, letting you compare it day-over-day against the same day last week. 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.