When I go to Settings - Data Usage, next to some of the apps it says "restricted." The only thing I can restrict is background data, which I've done for all the apps. But only some of them say restricted. What does this mean?
It is referring to the restriction of background data.
This list only shows apps that have used, or attempted to use, mobile data in the current cycle period, which is shown underneath 'Set mobile data limit' and should be set to match your billing period.