Screen Options Reset: Posts Edit set to 999, Get 502 error, how to fix?

Using the Screen Options feature (4.2.1) in the posts editor, I set the value to 999 (hoping to trash over 1000 drafts in a single swoop).

Now I can’t access that screen as I get a 502 error.

What is the easiest way to reset the display number?

All options I have found through searching seem to be outdated.

Thanks for your help!