Total. Amount of fuel is shown in the Fuel Tank - Current (T2). Fuel is stored in fuel tanks until those are full; then additional fuel goes to the cargo bay. This basically means that you can add fuel as long as there is space in cargo hold. By saying this, Fuel Tank - Current regularly goes over the Fuel Tank - Max value. Once the cargo hold is full, you cannot add any additional fuel, or supplies in general. Also, T16 has amount of fuel carried.