Hey @jordank, 
It could be due to one of these reasons: 
1. You have added it separately for both Desktop and Mobile but did not configure it in the block styles to show them individually on the devices. 
2. The template tag for unsubscribe section was added incorrectly which could also cause the Unsubscribe tag to appear twice in the same email. 

It would be more helpful if you could add some screenshot of the template in editor mode for both Desktop and Mobile and the final preview email.

Hi @sourabh thank you so much for responding! I think there was some sort of glitch going on that day, because when I logged on on a separate day, the double boxes appeared in my editing page, as well, and I was able to just delete them, and they no longer showed in my previews. Not sure what happened. Thanks again!!