If you have created a custom Civil 3D .NET report and added that in Toolbox and then set the units, precision value as shown in the picture below, but to your surprise when you generate the report you find the unit or precision value is not set as per the setting you opted in the 'Report Settings' dialogbox.
Reason for this is :
.NET reports use a combination of the Report Settings (for Client and Owner settings) and they use the drawing Ambient Settings for units, precision, and so on.
LandXML reports use the Report Settings for all settings, such as report header information, units, precision, and so on.
[Note - You can tell if a report is a LandXML-based report if the Export To XML Report dialog box is displayed when you run the report.]
To set the Precision, units for your custom .NET report, use the Drawing Ambient Settings as shown in the picture below -
Hope this is useful to you !