FIND:

        static $size = array(
            'large' => 'twelve columns',
            'lmedium' => 'nine columns',
            'medium' => 'nine columns'
        );

CHANGE IN:

        static $size = array(
            'large' => 'twelve columns',
            'lmedium' => 'eight columns',
            'medium' => 'eight columns'
        );


AGAIN SEARCH FOR:

echo '<div id="secondary" class="three columns  ' . $classes . '" role="complementary">';

CHANGE IN:

echo '<div id="secondary" class="four columns  ' . $classes . '" role="complementary">';