Based on what does the plugin remember users?

Hi,

I am making a quiz for subscriber roles only, and I am limiting the quiz to 1 time to be taken / per user.
So I did a test quiz and took it myself, the logged out and tried to access the quiz page, so the login form appears which says “This quiz is for logged in users only.” (and it is fine. But below that, I also get the notification that I already took the test and it is limited to 1 time, even if I am logged/signed out. How can I hide this for non logged in users? And based on what does the plugin recognize that it is me, even if I am not logged in? Is it the IP, cache, some kind of token…? If yes, can this be turned off somehow, and remember users only by email?

Thanks in advance