I believe it is actually not monotonic, which was a requirement for this library. That's why you end up using the high resolution timer which has a 10mhz clock

I believe it is actually not monotonic, which was a requirement for this library. That's why you end up using the high resolution timer which has a 10mhz clock rate instead. I ran into this problem trying to get better than 1us resolution for a daq system which was hooked up to custom GPS hardware which had better than 10ns resolution.