I've actually got the page up in Github and was about to make the quick edit to "fix it", but the proper administration guide link is already under "Primary Documentation".   Then I noticed the link under "Additional Documentation" appears to be a catch all for all directories/pages under the admin guide directory, with the other links under "Additional Documentation" being similar.  (and yes, that isn't working right as Juan pointed out).  It looks like the Additional Documentation links are a "Works as designed" more or less, but could definitely use some cleaning up in general?  I'd proceed as it looks like a quick cleanup, but I'm uncertain on design considerations here and the intent of the structure.  :)