Here is a sentence from a golf app's description:
This ball's Level 3 sidespin stat makes the most of a strong tailwind.
I know the lexical meaning of the word "stat", but cannot figure out its sense here.
Honestly, I am not entirely sure of the meaning here, without additional context. I am sure that "stat" is being used in the sense of "a numerical property", a sense which is derived from 'statistic", but I think you already knew or strongly suspected that.
I am fairly sure that a "Level 3 sidespin stat" is a very specific numerical property, having something to do with how the ball spins and thus how it reacts to air pressure and air movement, but I do not know jut what a "Level 3 sidespin stat" is, or how it would interact with a tailwind.
Since this is in the context of a simulation, not an attempt to measure and analyze the performance of a real ball, I think this 'stat" is a numerical property used to determine the behavior of the ball, in a way thought to simulate the behavior of a real ball.
One could rewrite the sentence as:
The numeric property X, which we have assigned to the simulated ball, increases the effect of a strong simulated tailwind more than other possible properties that might be used in the simulation.
This leaves one with no clue as to what X really is, but that does not decrease my level of knowledge significantly. I didn't know anyway. It leaves the essential meaning of the sentence unchanged, I think.
In gaming a "stat" is a number that represents the power of something. For example most role playing games will represent a characters "Strength" as a "stat", such that a "strength stat of 3" means you are less-strong than someone with "a strength stat of 5". If a character is more powerful, they "have higher stats".
You could also say that someone has "a level 5 strength stat", which is very close to how it's used in your example.
It implies that a level 1 and 2 "sidespin" ability are possible and that they wouldn't be as good as the level 3. This usage also implies that there are other abilities that balls can have, otherwise it would simply be called "a level 3 ball".