seo – Decrease in the number of valid pages in CSS

I have a very small site with only about 70 pages. About 4 days ago, GSC shows a 40% decrease in the validity of the number of indexed pages. When I check in which pages, it indicates the pages for which I always rank well.

Is this something that should worry me? Is there a bug in GSC or will these pages eventually be removed from Google search results?