IMO, fuel efficiency shown in the instrument cluster / Dashboard of Japanese cars brands isn't 100% authentic, as it shows reading on slightly higher side, when compared to manual calculations on tank-to-tank basis.
2ndly, I have observed that he fuel points aren't uniformly distributed throughout. When fuel tank is full, 1st point drops significantly late compared to other fuel points, like 1st takes more Kms covered than 2nd, 2nd more than 3rd, and so on...
3rdly, total fuel points may not be directly proportional to, or directly compared with total fuel capacity of car (including reserved fuel). If capacity is 50L, and points are 10, it may not mean that 1 point drops means that 5L fuel has been consumed.
I think things aren't like that...