I haven’t been able to replicate this on a fresh install of WordPress.
Have you altered any of the core theme files?
If so, I’d recommend making a backup of your site’s files and database, then remove the existing copy of the theme and download a fresh copy.
If it still doesn’t work, you might try disabling all plugins to see if that helps. If it still doesn’t work, you can try switching to a default theme like Twenty Seventeen. If you’re not able to limit the number of posts, it means something has gone wrong with your WordPress installation itself. In that case, you’ll want to make a new install or post in the Troubleshooting forum for help with the database:
https://www.ads-software.com/support/forum/how-to-and-troubleshooting/