public function display($message = null, $itemsLeftMessage = null) {
        $this->_verifyTotalValue();
        $this->_clearLine();
        $this->_renderProgress();

        if ($message) {
            echo self::SPACING;
            $itemsLeft = $this->_totalValue - $this->_currentValue;
            $itemsLeft = number_format($itemsLeft, 0, ',', '.');

            $output = $message . ', ' . sprintf($itemsLeftMessage, $itemsLeft);
            echo substr($output, 0, $this->_getMaximumMessageLength());
        }
    }