Users on the Firefox 3.6.x branch get an update offer for the latest Firefox 3.6.23 version. Users on later 4/5/6 branches that are on the release channel will get an update offer for Firefox 7.

Update offered to Firefox 3.6.23

• https://aus2.mozilla.org/update/3/Firefox/3.6.22/20110902133716/WINNT_x86-msvc/en-US/release/Windows_NT%205.1/default/default/update.xml
• https://aus2.mozilla.org/update/3/Firefox/3.6.21/20110830092825/WINNT_x86-msvc/en-US/release/Windows_NT%205.1/default/default/update.xml

Currently no updates to Firefox 7:

• https://aus3.mozilla.org/update/3/Firefox/5.0.1/20110707182747/WINNT_x86-msvc/en-US/release/Windows_NT%206.0/default/default/update.xml
• https://aus3.mozilla.org/update/3/Firefox/6.0.2/20110902133214/WINNT_x86-msvc/en-US/release/Windows_NT%206.0/default/default/update.xml

Thanks for the clarification. If I understand correctly this means Firefox has two development channels. Surely someone should see that this can lead to some confusion.

That is only the release channel.
Firefox has more update channels for developing new code with daily updates for testing.
There is the Aurora channel (8.0a2) and the Nightly channel (9.0a1) for testing new code.R When the 8.0 branch gets to the first beta release then that becomes the Beta channel and Aurora goes from 8 > 9 and Nightly from 9 > 10 to increase their version number.
The Aurora channel is six weeks behind on the Nightly channel to allow some baking of the code.

• https://developer.mozilla.org/devnews/index.php/2011/04/07/new-development-channels-and-repositories-for-rapid-releases/
• http://www.mozilla.com/en-US/firefox/channel/