Please find the below steps for making an item open as complimentary

Screenshot 1: Add menu item as open Item
check mark on Item Name Can be changed, Ask for Change Name, Item Price can be changed and Ask for Change Price. You may refer the below screenshot for the same

Screenshot 2: eZee POS Backoffice >> Click on 3 bullet points >> Option >> Display >> Receipt Settings 

Screenshot 3: Restart burrp and Punch open item as complimentary item but open item
Screenshot 4: Add new price for menu item – Punch item so it will ask to enter price

Screenshot 5: Select that item and set as complimentary item from the option

Screenshot 6: When you set complimentary rate, it will set item rate to zero as shown in below screenshot and you need to click on Finish Button and can make receipt

Screenshot 7: Now go to Reports view and open Complimentary report so it will show this item with modified rate into that report