The installed running software displays a "y" with dots above it in front of every file size.
Hmm, sounds like some kind of font issue. Folder Size actually does put "hidden" characters before every file size, so that the column will sort properly. These characters are supposed to have no visible form (like a "space" character), but I guess they are showing on your system. Have you replaced the default Windows font?
Yes, I had replaced the default font. (Since this bug was posted long time ago I've by now switched to Linux)