A hookup fee can be part of the Fuel service charges at some FBO's. In most of the cases, the Fuel service is auto-added to an order with 0 ltr. In this case the Hookup fee should not be charged until the uplift quantity is entered.
To do so, the hookup fee needs to be set to 'Take quantity from parent' and it needs to be set with ' Quantity band from parent calculator' plus calculator settings QuantityBetween=0 and 1. For receipt and invoice pdf, the hookup fee should also hide the unit and quantity and only show the service amount. This is needed because when 'taking quantity from parent' setting is used, the unit of measurement changes to liters and in reality the unit for this service per 'uplift'.