How to change the decimal places of AutoCAD Civil 3D contour labels

Changing the units precision of contour labels in Civil 3D is a process of many steps that are elusive and mysterious to anybody new to Civil 3D.  The very good news is that the steps required to change contour label precision are standard to all areas of Civil 3D.  This means that once you know how to intuitively change contour labels (including their precision), you will have made significant progress toward speaking the language of Civil 3D.  In other words, this is knowledge worth mastering.
The lovingly-crafted screen shot below shows how to change contour precision in 11 steps.  Click the image to see the full-size version.

 

Commentary on the steps

Step 1: Highlight a contour label.  Then right-click on it and choose Contour Label Line Properties...

Step 2: In the Properties palette, examine the Labels section.  Note that in that section you can turn off and change the display of the label line and any of the three types of labels: Major, Minor, and User (A high water contour with a label like "HW=1273.50" is an example of a use for User Contours).  Choose to Create/Edit the Surface Contour Label Style Major.

Step 3: In the Create/Edit box that appears (a standard box throughout Civil 3D), pick a style, then click the pencil/screen icon to edit the style shown.  You can use the down arrow next to the pencil/screen icon instead to do other things like copy the style or create a new one.

Step 4:  The Label Style Composer (a standard interface throughout Civil 3D) appears.  Make sure the Layout tab (standard throughout Civil 3D) is selected.

Step 5:  Make sure the Surface Elevation is the part of the label that is currently under construction.  When you become more familiar with Civil 3D, you will be able to add other Text, Lines, Blocks, and Direction Arrows to labels.  But for the moment, all you want to do is change the precision of the "Text" component that 1) has been conveniently named "Surface Elevation", 2) contains a formatted display of the Surface Elevation property that Civil 3D makes available to us, and 3) happens to be the only component of this label.

Step 6:  Click the ellipsis (...) to make an ellipsis button appear at the right edge of the Text, Contents field, then click the ellipsis button to open the Text Component Editor (standard throughout the Civil 3D interface).  In this editor, if you wanted to do more than just change the precision of the labels, you could add plain text (such as"HW=" for a high water contour) or other formatted pieces of data that Civil 3D makes available or that you create with Expressions of your own elsewhere in the Toolspace palette.

Step 7: Double-click the Surface Elevation formatting code in the dark pane on the right to highlight it and place all its values into the fields on the left side.

Step 8:  Select the desired precision on the left side.

Step 9:  Send the current selections to the highlighted cursor position in the right area using the insertion arrow.  The function of the insertion arrow is to insert a text element with the current formatting selections at the current cursor position.  Since we highlighted the existing Surface Elevation formatting code, it gets replaced with our insertion, just like in any word processor, which is more or less what the right area of the Text Component Editor is.

Step 10:  Note that the precision portion of the Surface Elevation formatting code has changed to the desired precision.  In the screen shot, it says "P2", so when we exit, the contour labels will display two decimal places of precision instead of the zero they are currently showing.

Step 11:  Finish by exiting all boxes.

The same screen shot is shown below without annotation.