code: public function getRemainingExtraTime($tags = null, $maxTime = 0, $target = TimePoint::TARGET_SERVER)
      {
          return max(0, $this->getExtraTime($maxTime) - $this->getConsumedExtraTime($tags, $maxTime, $target));
      }
docs: Gets the amount of remaining extra time
  @param string|array $tags A tag or a list of tags to filter
  @param integer $maxTime initial (total) timer value without extra time
  @param integer $target (server/client)
  @return float