It is possible to get synced clock with difference of 10ms maximum?

Hello,
I want to start working with your library and I have just read your recommendation for re-sync (calling initialize method frequently) each 1 hour to get sync of 1 second.
So if I want to keep sync with a difference of 10ms (maximum)- do I need to re-sync every 36000ms?!

and BTW, after initializing the "true time clock" on two devices- what the "true time clock" difference between them? because in my test is around 30-70ms. it is a lot not?