If I were to take a medium canister (8 oz fuel) on a 10-day trip not only would I NOT have 3.5 oz of fuel remaining on the last day, I likely would run out of fuel before the end of the trip. (I actually cook food, not just boil water). I can generally squeeze 8-9 days from the medium size canister. In your analysis the reason that the canister average is heavier than the alcohol is that the standard size of fuel canisters do not match the trip requirement. An apples to apples comparison would start by using up all the fuel in the canister, take that many days and compare the equivalent alcohol stove weights.