A simple metric that bowlers use to estimate their stroke is RPM, or revolutions per minute. The meaning of RPM is that the total revolutions that the ball goes on its way down the lane, weighted to the time of one minute.
Some of them think this by estimating the time it takes your ball to go down the lane (applying video recording) and calculating the number of revolutions (here is a youtube video describing this more, and a forum conversation about estimating revs) some other people think it with the speed or your shot and the number of revs.
Either way, the RPM calculate is a simple framework for which to relate various bowlers and their strokes.
Numerous beginning bowlers view the powerful RPMs of professional bowlers on TV and instantly think that more revs are essentially better.
In numerous cases, this is not the case: you don’t need to try to insist on yourself to throw more revs than comes naturally to you, and it’s not realistic to try to follow numerous of these pros.
The main part that moves your RPM, apart from the bowling ball you’re applying and the lane situations is the distance your fingers go during the release time.
If you’re really interested in learning more, then you can get an interesting discussion of rev rates here.