[26 Year Gap]

The key element is definite knowledge. As others have said, keeping a count gives you that definite knowledge. When I notice the clock is not moving and I am the trail official in the backcourt, I will verbalize "Clock! Clock!" while continuing my count as I near the table. Once I see the clock tick down [and this should be in the periphrery--you should not discontinue watching players], I know how much time has elapsed and it can be adjusted at the next dead ball. I will defer to others as to blowing the whistle if it is near the end of the game and the score is tight. I don't want to be that guy that blows the whistle for game over when the clock reads 0:05.3.

The table guy was using the seat of his pants and that just isn't good enough.