You can't format how a dimension is displayed, other than by setting it in your Model Info > Units settings - so if your precision is 0 there is no decimal reporting but a ~ will be added to the front of the number if it's no a whole number of meters.
The other way is to edit the dimension's text and type in what you want to see - but then it looses its ability to update whenever its connected geometry changes - because it will always show that edited text.
Incidentally, you can change a dimension's text AND keep the standardly formated 'numerical' part which will update, by using this syntax <>xxx - where the '<>' represents the dimension's standard output and the 'xxx' represents some text, like ' Site Dimension'; this additional text can come before the '<>', or after it, or on both sides...