97 % in this context means, that you reached an efficiency of 97 %. The town's demand was fully satisfied though. All towns consume the deliveries as long as you haven't satisfied all demands at once. This means, that 97 % of your deliveries went to the town's demand while the remaining 3 % were consumed during this process.

The 46,904 is your score for this completed town. You can improve it by getting a higher efficiency (using boosted trucks with B P L, having closeby storages, having less overfill for multi demand locations...) or using a smaller total tonnage. If you used 20t total tonnage to get a score of 50,000 points, you'd only get 25,000 points if you doubled the number of 20t trucks.

This is in fact totally normal.

Thank you very much for your answer ! This game (but is it a game ?), even with its ### interface, is quite... fascinating...

Some call it game... others a life time commitment...

Let me spoil something for you: Yes, the interface is terrible... until you got used to it. It's actually quite intuitive and well designed. You could compare it to an acquired taste like coffee or liquorice. It takes some time but afterwards you can't get enough of it.