Unable to remove included group permissions

Somehow my Anonymous Users Group (Users not logged-in) permissions includes all of the Administrators permissions; thereby giving all and sundry 'Take me now, Big Boy' access to my site. I've tried Administer Group, Advanced, Assign/Remove... to no avail, and can't find any other place to 'dis-include' the Admin permissions. Searching the forums/Googling bitweaver hasn't helped.

Any pointers would be greatly appreciated.