How do I fix a "Mismatched entity and/or field definitions" error on my configuration? I'm getting the following error on my Drupal 8 configuration page;

Entity/field definitions    Mismatched entity and/or field definitions
The following changes were detected in the entity type and field definitions.
Content

Update the node.rng_capacity field.
Update the node.rng_registrants_duplicate field.
Update the node.rng_registration_groups field.
Update the node.rng_registration_type field.
Update the node.rng_reply_to field.
Update the node.rng_status field.


I'm not sure what caused these issues or how to go about resolving them - I think they may be leftover fragments/elements from when I deleted a registration or entity type maybe?
You can solve this issue by two ways 
If you have Drush -

drush entity-updates


If you don't use Drush add following script before $response-&gt;send(); in index.php file(located in Drupal root folder) and reload the web page.

try {
  \Drupal::entityDefinitionUpdateManager()-&gt;applyUpdates();
}
catch (EntityStorageException $e) {
  print_r($e);
}


Then remove this code from index.php file.