For how I use it, it lives inbetween Spotlight and Numbers. Here's examples of the types of things I can recall using Numi for in the recent past: https://i.imgur.com/u4EdGbr.png

It's list of features is quite extensive: https://github.com/nikolaeu/numi/wiki/Documentation

Plus I don't mind paying for a simple, high-quality tool that I use all the time!