Per its DESCRIPTION, this Counter64 is the total number of accounted seconds in this lifetime bin, essentially the sum of Available and Unavailable seconds, used as a sanity check on coverage. Because this is a lifetime counter that only resets on an explicit clear, a reading here means the port has been tracked for that many seconds in total on this OC-n (SONET) port, accumulated over the port's entire service life, not merely since the last reboot. For example, if this Total Time doesn't roughly match how long the port has actually been in service, that mismatch is a sign the PM counters were reset or the card was swapped without anyone re-baselining the history.