(* ModCloth is a facebook page with about 1 million fans, so my potential audience should be much less than 1 million. see https://www.facebook.com/ModCloth)
But after I choose above interests, it shows Potential Audience for this ad: 9,000,000 people.
I just don't know the logic behind it, What is the logical conjunction between interests?
Facebook calculate the potential audience as below method?
The people who are interested in ModCloth plus people who are interested in corsets plus ......?
Please help, thank you