It sounds like what you did was correct. 100% crop should more accurately be termed a 1:1 crop. One image pixel maps directly to one screen pixel. Zooming your image to 100% and doing a screen grab is a common way to make it--it's pretty easy to see why it's commonly called a 100% crop.
The only thing that matters is the presentation of exactly one image pixel to exactly one pixel on the output device--in this case, the screen. Because it's really about pixels, and not size, resolution, etc., there are no PPI, DPI, inches, etc. involved.
Exactly. Dave, as long as you didn't resample/resize the image before or after cropping, it's a 100% crop and you're ok. Zooming in or out doesn't resample the image.Well, to be more accurate, it resizes on screen but not the file itself - not to confuse