In My Wholesale > Stock Management the wholesaler picks a location and sees a table with Name, Portion, Stock, Next Delivery Date and G&G Retail Price (the custom price, or --). Two buttons per line:

• Edit Stock - a Remove Stock movement with Quantity to Remove (must not exceed the stock; otherwise You only have N meals in stock and Save is hidden) and Reason of Movement.
• Edit Price - the window explains The current retail price for this meal at (Kitchen) is $X, Your default Surcharge is ($Y). This fee is an additional charge customers will pay to purchase this meal on the Grab & Go menu from you, and Your updated retail price for this meal is $Z. Turn on Change Retail Price ? and enter a Final Retail Price to override the calculated price for that meal/portion at this location, then Save.

The custom price is what Grab&Go customers pay at that wholesale location. The Default Surcharge itself is set under Configurations.