Firstly, open the stock unit definition.
After that, write the unit name and select quantity accuracy( choose one of digits for ex. 2 digits instead of none).
When you click on save, program shows you message.
Secondly, according to this message click on Admin(top of the panel).
Moreover, click on definitions and general settings.
Thirdly, click on stock settings. In the stock card settings , you will see accuracies.
Furthermore, select 2 digits and save it.
Finally, lets go back to the stock unit definitions and you can save your unit with 2 digits.