If you get 15.6521 it does not mean that this is the precision of getdate()!

Why do you think that @Time and @TimeEnd have succesiv values?

The conclusion, in my opinion, is the your system is very good (count is only 595 so only 595 times @Time and @TimeEnd are different, on my system is gets 18475), but the load of you system is very high, your processor is taken by another process from time to time so you get a very big value for the "precision" (in my case is 3.34344).