protected function getAggregationAuthorsCount(array $data) {
    $count = 0;
    $related_object = $data['related_object'][0];
    if (isset($related_object['target_type']) && $related_object['target_type'] === 'comment') {
      // Get related entity.
      $related_entity = $this->getActivityRelatedEntity($data);
      if (!empty($related_entity['target_id']) && !empty($related_entity['target_type'])) {
        $query = \Drupal::database()->select('comment_field_data', 'cfd');
        $query->addExpression('COUNT(DISTINCT cfd.uid)');
        $query->condition('cfd.status', 1);
        $query->condition('cfd.entity_type', $related_entity['target_type']);
        $query->condition('cfd.entity_id', $related_entity['target_id']);
        $count = $query->execute()->fetchField();
      }
    }
    return $count;
  }