It is possible to sell a part in a fractional quantity in Navigator.
To set this up, please go into Parts > View/Update record > enter the part number and click load, then in the Global tab, click the allow fractional quantities tick box and save the record.
This will then allow you to sell the part out at a fractional qty, please note, the system will only allow one decimal place, e.g 0.2 to be booked out, not 0.25.