The is no actual page for sa-learn. So if you do a search for sa-learn and click the Titles button you get this page. You need to do a search and click Text. Or you could just click the link below. 
[http://wiki.apache.org/spamassassin/FixingErrors?action=fullsearch&context=180&value=sa-learn&fullsearch=Text Search for sa-learn]