If you get the units wrong when you're importing a DXF/DWG file, you will end…
Vectorworks Tip 416 – DXF/DWG Dimensions
If you get the units wrong when you’re importing a DXF/DWG file, you will end up with information that is the incorrect size. This can be fixed, but it is better to get the units correct. One of the techniques I use is to check the scale settings to see if the scale looks about right for the units chosen.