To change price information during delays, click 
on the Delay form to open the Bunker Price form.
By default, the OFF HIRE Bunker Price is the TC/best known fuel price. If you want to use a different price, you can enter the price information.
You can override quantity and price defaults for waiting delays that are automatically generated by ports in the voyage itinerary. Values turn blue and are no longer updated on saving the voyage. From a right-click context menu, you can then click Use Bunkers from Portcall. All manually entered values are replaced by the default values, in black text.