Hey, @SAyon-1789!
What @ArashK-1211 said is correct. To put it a little more simply, the system needs a way to determine if the driver has stopped driving or if he is just stopping while in the middle of driving (e.g. at a light, etc.). When your driver stops driving, the app is counting down to 5 minutes. If the driver has been stopped for a full five minutes, it switches him over to an ON status from the time the vehicle stopped (5 minutes prior).
I recently made a short video on this, which you can check out here:
Understanding Drive and ON Logs in Geotab Drive
Best,
Joy B