Accessibility Error Messages

The documentation at tidy.sourceforge.net links to an excellent resource on
the error messages returned by Tidy:
http://www.aprompt.ca/Tidy/accessibilitychecks.html

I have a question, perhaps someone can answer.  How do Tidy's error messages
map to WCAG?  For instance, I see 13.10.1.1 which essentially matches WCAG
13.10 but what do the last two digits represent?

Thanks for any help you can provide.

Karl Groves
AIM/YIM: karlcore
Skype: eight.pistons
www.WebAccessStrategies.com