For some reason, the preferences for the Clean Archives Reloaded plugin for WordPress aren’t very substantial. The plugin hasn’t been updated in nearly three years and it doesn’t look like the plugin author intends on changing anything soon. The quickest way to remove the post and comment counts that appear parentheses to the months and posts respectively is to open the Plugin Editor in the WordPress dashboard, select the Clean Archives Plugin from the drop down menu in the upper right-hand corner of the screen, and then search for the following block of code:

// Generates the HTML output based on $atts array from the shortcode
function PostList( $atts = array() ) {
    global $wp_locale;

    // Set any missing $atts items to the defaults
    $atts = shortcode_atts(array(
        'usejs'        => get_option('car_usejs'),
        'monthorder'   => get_option('car_monthorder'),
        'postorder'    => get_option('car_postorder'),
        'postcount'    => '1',
        'commentcount' => '1',
    ), $atts);

In order to remove post and comment counts from the archives, simply replace the "1"‘s with "0"s. I’m not entirely sure why the plugin author didn’t just make it editable in the plugin’s preferences, considering that the majority of the code is already established for it. Perhaps a fork of the plugin is in order.