This code modifies the numbers in the selection for the search results (search form) - originally they're set to 10,20,30,40,50,60.

Custom Numbers for Search Results

/*
 * Custom Numbers for Search Results
 */

add_filter('ts_nr_options', 'custom_nr_options');

function custom_nr_options($args) {
  $args = array('12','24','36','48','60');
	
	return $args;
}