The Elevations From Surface option is unavailable if there are no surfaces in the drawing. If there is only one surface, that surface is automatically used to assign the elevation. If there is more then one surface, you are prompted to select the desired surface.
If no feature line rows are selected, the elevation of all points are updated. If the feature line is off of the surface, a warning message is displayed. If some elevations are updated, but one or more points are off of the surface, a message is displayed, indicating the number of points that could not be assigned elevations.
The feature line is updated in the drawing, and the grading is adjusted.