as John stated, text is always valued as inches, You can work in metric however, just beware of text!
With any custom attribute, even though you may have cm displayed, you must choose centimetres in the details and a metric or model units in the display if you want to include this in a report.
There are two functions that return inches,
FaceArea
Current
for facearea, you have to times the result 2.54*2.54
for Current, times the result by 2.54
So you can understand why some work in inches, but I still favor Metric
see this,