Not sure how many sizes of Torz there actually are, but I have only seen T10,15,20,25,30,35,40 which is 7 sizes. I think I saw a smaller one in a precision screwdriver set next to the other weird iPhone/watch ones like tiny pentalobes. But effectively Torx for all normal applications is one of 7 sizes, with T20 and T25 being probably 95% of all wood screws for building/carpentry applications.

I wasn’t aware that there could even be a “T17” or “T31” - simply because no one would ever do it. Increments of 5 is already close enough to some times guess wrong.