UPDATE: I tried using another browser, and it "solved" my concern. Maybe, even though I logged out, my website still picked up the log-in details enabling the codes to work on checkout (since it's the same browser). 

Hello, So I made a discount code for new subscribers. Paired with an email sign-up form and automated shopify email marketing algorithm, everything works seamlessly. However, when I tried checking out without logging-in (to make an account) and witho...