Trac download shows non existent revision?

I downloaded trunk from trac by going here:
http://trac.wsusoffline.net/browser/trunk
and clicking on 'Zip Archive' at the bottom of the page. The name of the archive is trunk-r600.zip but as far as I can see trac's latest revision is 599.
http://trac.wsusoffline.net/browser/trunk
and clicking on 'Zip Archive' at the bottom of the page. The name of the archive is trunk-r600.zip but as far as I can see trac's latest revision is 599.