-93.667
6.333 - 100 =-93.667
A thousandth is 0.001
You will look at the fourth digit, to the right of the one on the example above. If it is 5 or greater, round up. Otherwise round down.
-93.667
The number after 7 is 0.
0 < 5
Therefore we round down, leaving the 7 as it is
-93.667
