Non-caring customer "care"

On 20 February 2024 an Avis rental vehicle was dropped off at the panel beaters for me whilst my vehicle was in for repairs. Vehicle was clean, but definitely not spotless and all looked good. I did the walk around with the Avis driver and asked him whether the vehicle was full of petrol. He said yes, barring the 4 kilometres they had to drive to the panel beaters. After driving off, within 10 km, the digital petrol gauge dropped to the 7/8th position. I did not drive the vehicle at all, besides to my house and then back to the panel beaters on March 2024. I stopped by a car wash which washed the car and was spotless. I then stopped at a petrol station and told them to fill the vehicle up. Now I travelled only 122 km, so therefore I am expecting to fil up 10 litres at most (assuming 10l / 100km, which the polo should give me 6.7l / 100km - I drive carefully). It filled up 25 litres. I complained, and what is Avis's response: "We fill it up to the click at the pumps, therefore it was correct". This is just plain *******.