How does this work?

The GitHub Contribution Checker uses the GitHub API to check the documented criteria used for counting a commit as a contribution. It is currently only possible to check commits authored in public repositories.

The following OAuth scopes are requested when you are prompted to authorize the application:

Scope	Reason
user:email	Read-only access to the email addresses you have added to your GitHub account is required when checking whether the email address used to author a commit has been added to your GitHub account.
read:org	Read-only access to your GitHub organization membership is required when checking whether you are a member of the organization which owns a repository in which you have authored a commit.