Pull requests
A pull request is a proposed code change for review. On the canvas, work on its way to your Mac shows in the Shipping widget, which answers one question: is stuff shipping?
Follow the change
The card shows how many items reached your Mac today. On the way lists work that has started but hasn't reached your Mac yet. Each row shows its stage as Crew on this Mac reports it: Building, Review, Merged or On your Mac. Merged does not yet mean installed on your Mac.
Check failing marks a row whose check failed, and those rows come first. Fix the failing check writes a request to your Chief in its message box; nothing is sent until you send it.
If Crew on this Mac hasn't reported this work, the list isn't drawn. A missing list is not a count of zero.
A company's GitHub pull requests
Crew can list a project's open GitHub pull requests in that project's Shipping widget at its largest sizes, each with its number, title and how many checks passed. It reads them read-only, through the GitHub account already signed in to GitHub's command-line tool on your Mac; the token stays with that tool, and Crew writes nothing to GitHub.
This connection isn't switched on in this version yet, so no GitHub pull requests appear.