What is duplicate registration based on?

I have "prevent duplicate registration" marked yes, but multiple registrations can be made using the same name and email address. What gets prevented by marking this button yes?

Hi Jim

In the current version, the extension will only check based on ID of the user, that mean it only works if the user is logged in. In the next release, I will improve it so that it will check based on user email as well, so prevent duplicate registration will actual works for the public users.

Regards,

Tuan