Need help with F8 theme, Number of post on home page

Currently I am working on a photography website ->

https://www.3680photography.com/content/

On the index page, currently 10 default post show. I’ve been trying to get 12 total to display to fix the symmetric and aesthetic feel of the site.

I’ve browsed through the index.php, home.php and archive.php but can’t really seem to figure out how to fix this issue.

Any help would be greatly appreciated!