Please follow the steps for assign a percentage to the returns I get from the retailer
Login to the Back Office > go to ‘Settings’ from the left menu, click on ‘Shop Settings’ in the submenu of ‘Settings’ to enable ‘Order Return Rules’ > click on ‘Save Settings’.
Once the tab ‘Order Return Rules’ is enabled, please set your % according to the reason. Click on the ‘Edit’ button, next to the reason to save the % rules.