I get that a red x means it's not being shared, but what's the difference between a green checkmark and a fully green box? I've noticed that if you sort the column according to the shared status, the red boxes will be on the bottom, the green checks will be in the middle, and the green boxes will be on top. This does signify that there is some difference between a green check and a green box.
So what's the difference? Anyone got any clues?