The Units area for a dimensioned feature (Insert | Dimension) enables you to choose between the following two options:
Inch = Inches
MM = Millimeters
When you create a dimension (either legacy or FCF) for the first time, PC-DMIS uses the measurement unit of the current measurement routine. Thereafter, PC-DMIS recalls what you selected on your last created dimension when you next open a dimension or the XactMeasure GD&T dialog box.