I was wondering if the software weren't very bright, implementing "slower" and "faster" one tick at a time until it matched whatever the input signal is. No particular reason other than the suspicion that they haven't put much thought or effort into it. (I've only ever seen them change by one, but I haven't seen a lot of changes either -- normally you'd have to be quick and lucky to notice them, after all.) Maybe it's a time delay. I wonder what the input is.