To enter new offset values:
Click the Offsets button from the Construct Plane dialog box (Insert | Feature | Constructed | Plane) to open the Plane Offsets dialog box.
In the Offset column, click on the 0.000000 value (or current value) to select it.
Type a new value.
Press the Enter key.
Click Calculate to update the nominal values based on any offset(s) you chose.
Click OK to save the offset.