This counts seconds during which the TDM path carried over this pseudowire was considered available. Comparing ASP against TTP for this PW gives the actual path-layer availability percentage for the service, the figure that belongs in an SLA report for the emulated circuit rather than the service-layer UAS/AS pair alone -- and this specific object covers a closed 15-minute history bin -- a fixed, final count for one completed interval rather than something still changing. For example, over that completed 15-minute bin, this pseudowire might show this counter at 500 -- a concrete count the admin can trend against neighboring bins to judge whether the condition it reflects is worsening.