The 0 you add on the end is not needed so writing 6.52 instead of 6.520 is more time-efficient and quicker. They both still mean the same thing though. You can add as many 0s as you want but only to the end. If you write 6.520000000000000000000000000000000000000000000, it still means 6.52. The zeros at the end are pointless. If you want to save time and energy, DON'T PUT EXTRA ZEROS. Hope this helps :D