How much fuel your engine burns at full power, in gallons and liters per hour, and the pump rating that covers it with a safety margin.
Pumps are rated at a specific pressure and voltage, and flow drops as pressure rises. Check the pump's flow chart at your actual fuel pressure, adding boost if the regulator is boost-referenced.
BSFC is how many pounds of fuel the engine burns per horsepower per hour. The defaults match the fuel injector calculator: about 0.50 for naturally aspirated gasoline, 0.60 boosted, 0.70 on E85 and 0.80 on boosted E85. Gasoline weighs about 6.1 lb per gallon and E85 about 6.6.
The margin covers pump wear, heat and voltage drop. Many builders size for 20 to 30% more than the engine needs.