When you define the labels, there should be a pane on the right side with some formatting language. You can't edit the formatting directly, but you can change the parameters in the left pane. You then highlight the label on the right side and press the arrow that points right, which replaces the old formatting with the new formatting. It took me much too long to figure that one out, because it's not obvious.
To be a bit more specific, there should be a Precision parameter for the label, and its value should now be 10. Change it to 1, highlight the old label format, and update it.
For future reference, you want to update your software profile to show Civil 3D, and you want to post C3D-specific questions in the C3D subforum (it's in the "Vertical Products" forum).