Does it really matter how many kilometers it really has done? It's a used car, with an aftermarket cluster from Japan.
It may have done 5,000km more or 50,000km more than what the current cluster states. The main thing you should be looking at is the condition of the car.
The owner has obviously spent a large sum of money having it built so it runs properly. I'm sure it's realiable as well.
Good luck with the sale, wish I had the money for it. I would get this over a new Infiniti.