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 rolls up the entire day so far rather than one short interval, 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, cumulated across the entire day so far rather than during one short polling window. 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.