In my Stack Overflow profile there is a window on the left that shows some of the other communities I'm active on. When I click 'edit', a new menu appears that contains an option called 'hide communities'. When I click it, a list with communities is loaded and I'm able to hide communities from the list that is displayed on my profile page.
Above the list it says
Showing 12 community out of 31 visible communities
Why am I only able to hide 12 of the 31 communities and why can't I see all 31 of them on my profile page?