Adding and Editing Unit of Measure
You can add units or edit them within a unit of measure class. When you add a new unit to the class, a conversion to a unit within that class and an abbreviation for the new unit need to be added.
For example, the class "length" has a canonical unit called "meter." When you add the new unit "inch," an abbreviation "in" and a conversion factor to meters of the value "0.0254" needs to be added.