404 detection notice

I’m up to 638 events and all of them are “404 detection – notice”. I’m getting links to onesignal plugin from the staging area I created a few months ago, readme.txt files I never uploaded, every author page and the list goes on.

What are these “notices” Do I have to create 301 redirects for every one of them?

The page I need help with: [log in to see the link]