Number of posts displaying on a blog page

On my site’s page http://tpn.wpengine.com/blog/

there are only 4 posts displaying at once on the page. I would like to have more than this. In Settings > Reading, I have the option of setting the maximum amount of posts per blog page, but I don’t see an option for setting the minimum amount of posts per blog page to display. I would like a minimum of 12 posts to display on my blog page.