Doing some testing, I found that it's the .xmp files that are counting as unkown!
I opened a folder (I've since delete the test folder that I posted the screenshot of), and removed all the .xmp files and the count showed 12+12 image files, for the 12 raf and jpg files in the folder. I added 1 .xmp file back in and the "1 unknown" status showed back up.
Would it matter that I have the .xmp extension mapped to Notepad, so that it opens when I double click on the file?