What it is for. The link registry for installers: copy links, resend, revoke and delete.
What you see. Counts of installers with access, then a row each with the link, status and actions.
The Clean Duplicates button. It exists because duplicate access records happen often enough to need it. If a banner appears offering it, take it — duplicates are why an installer sometimes reports that an old link still works after you revoked one.