I’m on my computer now, so I’ll type out some more detail if you’re interested. To reiterate, I’m just going off memory and it was two weeks ago so I could very well be making stuff up…

The pre-filled input box asked for each blocked instance to go on a new line, so:

lemmy.world  
lemmy.ml  
lemmygrad.ml  
hexbear.net  
lemmy.zip  
piefed.social  
etc...  

I deleted all of the defaults and that was it. I’ll put a screenshot of the settings page that’s available to admins below: