Modifying Tile Width on Codium Grid Template

Hello,

We are working on creating a blog for our website that is based on the Codium Grid Template, and on the main page I would like to change the width of the tiles that show each post (see attached image). One of our tweaks caused them to become narrower than they should be, and I would like to fix them.

You can view the page I am talking about at CommotionEngine.com/blog

Thanks,
Micah