This read-only Unsigned32 reports the number of Out-of-Sync Seconds recorded since the BERT test started, per its description. An administrator watches this as a measure of how much total time the link spent unable to maintain pattern synchronization during the test, a more severe condition than ordinary errored seconds. For example, a test with a nonzero bertTestStreamMonOOSSsSinceStart alongside a high bertTestStreamMonSyncCounts value would tell an operator the link struggled to stay locked throughout the run, not just to pass individual bits cleanly.