Hello! The suggested size is expressed in points (pts!) not pixels. A font rendered at 12 points will be shown 1:1 on screen. So, in the case of Torch, it will have a cap height (the height of uppercase letters!) of 6px. 24 points will scale it 2x , 36 will be 3x and so on.
It's important to use pixel fonts at the correct point size to avoid uneven upscaling (that will look horrible and create artifacts, like with pixelart in general!). If you want, you can try with one of my free fonts before committing to a purchase. What about Yolk? https://somepx.itch.io/free-font-yolk
Let me know if I can help in any other way, no problem at all.