wordpress dosyaların içinde wp-includes/widgets.php dosyasını açıp bu kodu bul;

function wp_widget_recent_entries($args) {
    if ( '%BEG_OF_TITLE%' != $args['before_title'] ) {
        if ( $output = wp_cache_get('widget_recent_entries', 'widget') )
            return print($output);
        ob_start();
    }

    extract($args);
    $options = get_option('widget_recent_entries');
    $title = empty($options['title']) ? __('Recent Posts') : apply_filters('widget_title', $options['title']);
    if ( !$number = (int) $options['number'] )
        $number = 10;
    else if ( $number < 1 )
        $number = 1;
    else if ( $number > 15 )
        $number = 15;

    $r = new WP_Query(array('showposts' => $number, 'what_to_show' => 'posts', 'nopaging' => 0, 'post_status' => 'publish', 'caller_get_posts' => 1));
    if ($r->have_posts()) :
?>

bu kod ile değiştir, artık 25 adet olacak üst sınır;

function wp_widget_recent_entries($args) {
    if ( '%BEG_OF_TITLE%' != $args['before_title'] ) {
        if ( $output = wp_cache_get('widget_recent_entries', 'widget') )
            return print($output);
        ob_start();
    }

    extract($args);
    $options = get_option('widget_recent_entries');
    $title = empty($options['title']) ? __('Recent Posts') : apply_filters('widget_title', $options['title']);
    if ( !$number = (int) $options['number'] )
        $number = 10;
    else if ( $number < 1 )
        $number = 1;
    else if ( $number > 25 )
        $number = 25;

    $r = new WP_Query(array('showposts' => $number, 'what_to_show' => 'posts', 'nopaging' => 0, 'post_status' => 'publish', 'caller_get_posts' => 1));
    if ($r->have_posts()) :
?>

sonra panelden ayarlarken parantez içinde hala en fazla 15 yazar, onu değiştirmek için yine aynı dosyada bunu bul;

            <p><label for="recent-entries-title"><?php _e('Title:'); ?> <input class="widefat" id="recent-entries-title" name="recent-entries-title" type="text" value="<?php echo $title; ?>" /></label></p>
            <p>
                <label for="recent-entries-number"><?php _e('Number of posts to show:'); ?> <input style="width: 25px; text-align: center;" id="recent-entries-number" name="recent-entries-number" type="text" value="<?php echo $number; ?>" /></label>
                <br />
                <small><?php _e('(at most 15)'); ?></small>
            </p>
            <input type="hidden" id="recent-entries-submit" name="recent-entries-submit" value="1" />

bununla değiştir;

            <p><label for="recent-entries-title"><?php _e('Title:'); ?> <input class="widefat" id="recent-entries-title" name="recent-entries-title" type="text" value="<?php echo $title; ?>" /></label></p>
            <p>
                <label for="recent-entries-number"><?php _e('Number of posts to show:'); ?> <input style="width: 25px; text-align: center;" id="recent-entries-number" name="recent-entries-number" type="text" value="<?php echo $number; ?>" /></label>
                <br />
                <small><?php _e('(en fazla 25)'); ?></small>
            </p>
            <input type="hidden" id="recent-entries-submit" name="recent-entries-submit" value="1" />

artık olmuş olması gerekiyor. bir bak dene bakalım.