Number of posts on category pages

I’m using the Clickbump theme and want to change the number of post excerpts that are displayed on category pages. At the moment it just shows 1 post excerpt. Looking at the code there should be an option somewhere in the theme settings to change this but there doesn’t seem to be and I’m only able to change the number of posts for the home page. That being the case, what changes would I need to make to the code below?

if(is_front_page() && get_option('cb2_blog_home') && get_option('cb2_blog_home_count')) $numberposts = get_option('cb2_blog_home_count') ? get_option('cb2_blog_home_count') : $numberposts;
	elseif(is_category() && get_option('cb2_blog_inner_count')) $numberposts = get_option('cb2_blog_inner_count') ? get_option('cb2_blog_inner_count') : $numberposts;