Posts per page in admin area

I have created a custom post type called fotopost. The trouble I have is that when editing fotoposts (wp-admin/edit.php?post_type=fotoblog), the list displays only 5 posts. In the page settings (on top of this page) the posts per page options shows 20. I tried changing this value, but no matter what I do, the edit page shows only 5 posts. Btw, pagination is in place and working, so I can access all my custom posts, but I would like to display 20 posts at a time.

Any idea what happens?