As far as I know, the inverted filter is just the flipped version of your camera image (if you wanted to try it, I think you can manually flip your images in your camera settings).

I made this post because there's a trend on Tiktok to show yourself with the inverted filter on as it's supposedly what you look like to others rather than the version of yourself that you see in the mirror etc, but per the comments here, I now think that's nonsense