The default units are set by the templates when installing RFEM or RSTAB (see the Selecting Region and Unit System image): If you selected '[US] United States of America', imperial units are set. Metric units are used for all other languages.
To adjust the units and decimal places, click the
button in the bottom left corner of the 'Base Data' dialog box (see the
'Main' Tab
image).
Select the unit category first. Then you can adjust the unit by clicking text box and opening the list of units.