custom scope in structural search

Hi

I'm trying to remove all comments in a project and then i selected the comment template in the structural replace window.
Then I created a custom scope where i have excluded all, just letting classes on which i want this replacement occurs.
The windows is telling i have  selected 579 of 76194 : so  it's ok

But when  process the find it doen't work. It is lookking for all classes in the project including libraries and finds 24291 usages ...

maybe i'm doing someting wrong or a missed a parameter ?

thanks for any help