FWIW, those numbers are based on "the number of unique contributors (users who pushed code, opened or commented on an issue or PR)" to a project in those orgs.

FWIW, those numbers are based on "the number of unique contributors (users who pushed code, opened or commented on an issue or PR)" to a project in those orgs. So not really a measure of those companies' contributions to open source (it counts any action from any user, not just someone from those orgs), but companies also have more than one org (you can see the problem with all the articles covering this from the fact that both angular and google are in the top ten list...).