public function decrement($key, $offset = 1)
    {
        $duration = $this->_config['duration'];
        $key = $this->_key($key);

        $value = (int)$this->_Redis->decrBy($key, $offset);
        if ($duration > 0) {
            $this->_Redis->setTimeout($key, $duration);
        }

        return $value;
    }