When I checked this morning, my Wally special was 10 off, registering 65%. However, I wasn't sure I did it right because my salt was not slushy looking, so I redid it and came up with that slush look. I also took apart the hygrometer and put two larger holes on the side. Right now it's reading 74%, so I think it's ok.
I'll probably still buy a better one, but this should get me by for a while.