Terrorism …..

I was browsing the net when I came across this article talking about a potential 9/11 10th anniversary attack in the U.S. I certainly hope that this would not be true

However I am confused after reading the article. The article quotes a person from Homeland security as saying “In this instance, it’s accurate that there is specific, credible but unconfirmed threat information.’’

If its accurate , credible and specific, how the heck can it be un-confirmed ????? I can’t figure this one out, can you ?