If I wanted to mix a litre (1000cc) of fuel with 12.8% nitro, 21.4 % oil and 65.8% methanol I'd pour 128cc of nitro, 214cc of oil and 658cc of methanol into a container. See a pattern there? And I didn't need a calculator to figure it out
If I'd wanted to mix 4 litres of fuel (a bit over 1 US gallon) I'd have multiplied each figure by 4.