"Only the most recent 50 pages are shown above" when trying to edit access levels?

Under membership > access levels, I clicked to edit one of the access levels, and looked under the "pages" option I had previously set. I needed to enable certain pages to be viewed by the access level. I noticed it mysteriously wasn't in the list. When I looked at bottom of the pages option, it said: "Only the most recent 50 pages are shown above."

I tried to click "update" on the page that wasn't in the list, hoping that would make it appear, and it didn't. It was only until I deleted some pages that it appeared. The problem is, there's only one or two more pages I can delete, and a lot more pages that need to show up on that list.

Is there anything else I can do besides delete pages to make the list complete? I'm finding this very frustrating, and to me it seems that all the pages should be listed, not just a certain number. Is there any way I could increase that number?