This read-only Gauge32, measured in milliseconds, reports the maximum audio/video out-of-sync delay measured since the beginning of a currently active call session. An admin checks this to see how badly lip-sync has drifted at its worst point so far in a call that is still ongoing. A live call reporting a large max out-of-sync delay would let the admin address a lip-sync problem for the remainder of that call rather than only learning about it afterward.