In the “Edit stock” page, stock of any item may be edited manually. There are 4 buttons at the left of the second table. The “Missing stock”, “Sample given”, and “Wasted/defected” buttons edits stock of any item negatively. And the “Add stock” button edits stock positively.
Click on any of the buttons, it will create a row in the table. Select the material batch which will be edited, and write the amount. The remaining stock will be automatically updated.