In- and Exclude Filter definitions are relative to the root of your base locations.
If Main is one of your base-locations, you need to exclude \FolderA\A_Exclude\
not just \A_Exclude\
That makes sense. But, is it possible to wildcard it? I have many folders on the FolderA level (C, D, etc.) and all have the folder I want to exclude under it and more are created every day. They are basically temporary folders that I don't need backed up.