code: public function getConsumedExtraTime($tags = null, $maxTime = 0, $target = TimePoint::TARGET_SERVER)
      {
          if ($maxTime) {
              $totalConsumed = $this->compute($tags, $target);
              $consumedExtraTime = $totalConsumed - $maxTime < 0 ? 0 : $totalConsumed - $maxTime;
              $this->setConsumedExtraTime($consumedExtraTime)->save();
          }
          return $this->consumedExtraTime;
      }
docs: Gets the amount of already consumed extra time. If tags are provided, only take care of the related 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
  @throws