>>717096259When a user logs into the Steam client, it runs some logic that attempts to determine if a user is logging in from a new machine, or an upgraded machine. If that machine is likely to be the users "primary" system, basically if it knows if a user has other devices it will try to present on their Windows box. If it isn't on that system, it can be a while before the monthly survey check decides it can present on a different system.
If it passes all the checks, it presents to the user, and if the user opts into the survey then it records the details of that particular system, and submits them for inclusion.
This obviously has a lot of problems. The survey logic has a bad habit of over counting users it sees on "new Windows systems" more frequently, like Chinese net cafe users. While under counting users on platforms other than Windows since it is less likely to present on "secondary" systems. If you recently switched to Linux after using Windows for years, the survey won't actually count you as having switched until it actually presents the survey to you on a Linux machine.