Number of thumbnails on homepage

I am attempting to change the number of thumbnails on the home page from 9 to 16. I have successfully changed the thumbnails size to accomodate the 16. I have found the following information on the steps to accomplish it at https://wptheming.com/2010/07/portfolio-theme/

“Change: $query->set( ‘posts_per_page’, ’9′ ) in functions.php, and: ‘posts_per_page’ => 9, in content-portfolio.php. Portfolio+ has an option for infinite scroll.”

However, if I change the 9 to 16, it breaks the site and I receive the basic 500 WP error. It also looks like the above code might be slightly different from the version I am running(1.6). Is it possible the code above might need to be slightly modified for the latest revision?

Thanks for your help.