The numbers on le folders correspond to le Site ID of chaque spécifique site in IIS. If you go into Internet Manager you can see le Site ID's by clicking on le Sites node in le navigation pane.
So, si a site has ID 1 its log folder name is W3SVC1, ID2 = W3SVC2, etc.
You could aussi review %WinDir%\System32\Inetsrv\Config\applicationHost.Config, qui contains information about tous of le sites. C'est XML format. You'll want to cherchez <site> nodes in le XML qui contain an id attribute. Ceci est le aforementioned Site ID of that spécifique site et will align avec le number in le log folder.
`<site name="Default Web Site" id="1">