Okay maybe this has to be a bug but when I went to check out books just now that said 7 days. I went and changed my limit from 14 to 21 and reloaded the page and now those titles say 21 days!
I change it back to 14 and reloaded again and now it says 14 days.
So I think it's a bug. I don't think it means what we think it means by limiting the amount of days a book can be checked out or it isn't fully implemented yet.
Could it just be badly worded but really mean how many days you have your checkout limit set at? How confusing!