This read-only Integer32 reports the elapsed time of the BERT test for this stream in seconds, per its description. An administrator polls this during a long-running test to check progress without waiting for it to complete, especially useful for tests configured with a multi-hour bertControlDuration. For example, an operator checking in on an overnight soak test partway through would read bertTestStreamMonElapsedTime to confirm it's roughly on schedule to finish by morning.