function.php

<?php

// Don't include above <?php

add_filter( 'genesis_post_comments_shortcode', 'prefix_post_comments_shortcode' );
/**
 * Amend the post comments shortcode to add extra markup for styling.
 *
 * @author Gary Jones
 * @link   http://gamajo.com/style-comment-number/
 *
 * @param string $output HTML markup.
 *
 * @return string HTML markup.
 */
function prefix_post_comments_shortcode( $output ) {
    return preg_replace( '/#comments"\>(\d+) Comment/', '#comments"><span class="entry-comments-number">$1</span> Comment', $output );
}