Why do only some repositories show up in Unsubmitted Packages?
After you login via GitHub to the My page, your public repositories will be scanned. Your repositories that GitHub has tagged as containing Python will be searched for a setup.py and if one is found, that repository is eligible for submittal and will appear in the Unsubmitted Packages table. For general help with packages, see the official Packaging Python Projects page
What happens when the Submit button is pushed?
Your repository is cloned and then python setup.py sdist --formats gztar is executed to generate distribution files for your package. Those distribution files are the added to the index, a web page is created based on your Readme.md file (the first line is removed and the rest is converted from Markdown to HTML), the first 30 words past the first line of your Readme.md are used for search purposes, your package will start getting downloads tracked, and it will appear in the Submitted Packages table.
What happens when the Update button is pushed?
The same exact steps as when the Submit button is pushed. If you have incremented the version number in submit.py, both old versions and the new one will be available on the index.
What happens when the Remove button is pushed?
Your package is removed from the index, as is its web page. Download statistics are kept, although not accessible, in case the package is re-submitted later.