Note that according to standard racing rules, this means you end up driving 10 laps in total, because the last incomplete lap is driven to completion by every driver. The rest of the extra fuel comes from adding a safety buffer, as various things can make you use a bit more fuel than expected: the bit of extra driving leading up to the start of the race, racing incidents and consequent damage to the car, difference in driving style, fighting other cars a lot, needing to carry the extra weight of enough fuel for a whole race compared to the practice fuel load where 2.73 l/lap was measured.
What I really appreciate in GPT-4 is that even though the question looks like a simple math problem, it actually took these real world considerations into account when answering.