This value reports how many seconds have elapsed since the UPS most recently switched to running on battery power, or since the management agent last restarted, whichever is shorter, and returns zero when the UPS is on utility power. Admins use it to gauge how long an outage has lasted and to trigger alerts or graceful-shutdown scripts once the duration crosses a threshold. A reading of 300 would mean the UPS has been running on battery for 5 minutes since the last utility failure.