Smart Pagination Being Overridden by Default WP Reading Settings

I’m setting the WP_Query setting in the PG WP Action to 8 posts per page:
When I get to the 3rd page it gives me a 404. If I go into the WordPress admin and go to Settings → Reading and also change that to 8 then the 3rd page works, however I thought that the posts_per_page should override the default settings in WP.

This is happening on a category archive page, but even if I put 8 in the pages_per_archive box it does not change anything.

I think the Smart Pagination action in PG is not working properly.