Include Category for the related article

Hi everybody,

When I try to include category (7 category : "14,15,16,17,18,19,23") for the "Most Read Articles" Tab, it's ok, but when I try to include this categories for the "Related Articles" Tab, others categories are also include.

Did I make a mistake ?

Thanks.

EDIT: There are always the same related article in many articles. And these articles are in the category "12".