I think it's because Samsung accounts consider different browsers as seperate devices. For example, if you sign in through the settings app, Chrome for Android, and Firefox on PC, your account lists 3 "devices".
If you're still worried, feel free to remove all your trusted devices. The only thing that trusting a device does is let you skip two-factor authentication the next time you sign in on that device/browser. So the only consequence of removing trusted devices would be the mild inconvenience of having to type an extra 6 digits if you ever sign out and back in to your account.