Hey Jempy,
The app gets tyre wear data from the game in the range 0-100%, and that's what most other apps show, without any changes.
However, as Stefano (or maybe it was Aris, not sure) mentioned on multiple occasions, anything below 94% is borderline undriveable. So, in order to make it more logical, to increase the precision and save screen space, by default I treat 94% (and everything below 94%) as 0% and scale everything by 16 (16.66 actually, because the interval 94-100% is 16.66 times shorter than 0-100%).
This way, the interval 94-100% as the game reports it becomes 0-100% as Sidekick displays it. In my opinion, this makes the data more sensible. For example 96.2% (as the game reports it) doesn't seem like anything you should worry about while driving, but once scaled it becomes ~36%, and it makes you realize you've actually worn the tyre quite a bit. As an additional bonus, you don't have to process the decimals with your brain/eyes while driving and it takes up less space.
If for whatever reason you don't like this scale, you can decrease the wear scale to 8 for example, and that would make Sidekick take into account twice longer interval (88-100% as the game reports it), and previous example of 96.2% (as the game reports it) would become ~67% as displayed by Sidekick.
If you set the wear scale to 1, Sidekick displays the exact data received by the game, without any scaling, although without any decimal points, so quite imprecise.
The colors however, always follow Kunos' official tyre app where the wear turns yellow below 98% as the game reports it (this will happen at 66% with wear scale 16 in Sidekick) and red below 96% as the game reports it (this will happen at 33% with wear scale 16 in Sidekick) regardless of wear scale. This is one more reason why 16 is default, since it gives nice equal thirds for coloring where 0-33% will be red, 33-66% will be yellow, and 66-100% is green. The wear colors are affected by the scale only in a sense that you will "hit" the color changes on higher numbers as Sidekick displays them. It's important to comprehend that no tyre wear data is actually ever changed, but only scaled for convenience, and that's why the color changes will happen independently (and always at the same time) of the actual wear numbers shown, which are dependent on the currently set wear scale.
Hopefully this was clear enough.