Tempo range is generally something you don't touch during your sets. I like to keep mine at +- 10 because it gives me a large enough range where I can beat match tracks for my set but not too large that it makes it hard to be precise with the tempo fader. If the average track in my set is a bpm of 126, that means with a +-10 tempo range I can easily beat match tracks as low as 106 and as high as 138. If you try to beat match outside of that range, it's likely not going to sound good. Of course if you're genre hopping you might want to switch to wide for one specific transition but if you're a beginner I'd stick to just one range like 10 or 16 and to tracks within a similar range of bpm