a players shot time

[GD73]

often wondered how they calculate the speed that a player plays at

if ronnie plays at 16 sec - then when does the clock start?

when he gets to the table? hand on the table?, down on the shot in the address position?

[jrc750]

When the previous ball comes to rest that's when shot starts

[cantpotforshíte]

I reckon JRC is right.
But in the instance of a safety battle, what should happen is that the shot clock should start when the last player gets out of the way completely. Most players really hog the table these days and delay the incoming striker. I'm sure it's a psychological ploy to stop the momentum of the incomer. If I were the incoming player I'd wait until the last player was sat in his chair, then race to the table looking the business. I reckon that'd stop the hogging nonsense.
In any case, it's only a TV statistic, nothing to do with World Snooker (apart from in one new 'ranking event') so doesn't really matter.