diff --git a/core/core.api.php b/core/core.api.php
index ee32e87..7af4c08 100644
--- a/core/core.api.php
+++ b/core/core.api.php
@@ -283,13 +283,9 @@
  *
  * The first task in using the simple configuration API is to define the
  * configuration file structure, file name, and schema of your settings (see
- * @ref sec_yaml above). Once you have done that, you can retrieve the
- * active configuration object that corresponds to configuration file
- * mymodule.foo.yml with a call to:
- * @code
- * $config = \Drupal::config('mymodule.foo');
- * @endcode
- *
+ * @ref sec_yaml above). To change configuration you will need to get an
+ * instance of Config by making a call to getEditable() on the config factory.
+ * You can do so like this:
  * This will be an object of class \Drupal\Core\Config\Config, which has methods
  * for getting and setting configuration information.  For instance, if your
  * YAML file structure looks like this:
@@ -307,11 +303,20 @@
  * $bar = $config->get('bar');
  * // Get one element of the array.
  * $bar_baz = $config->get('bar.baz');
- * // Update a value. Nesting works the same as get().
- * $config->set('bar.baz', 'string2');
- * // Nothing actually happens with set() until you call save().
- * $config->save();
+ *
+ * @code
+ * $config = \Drupal::service('config.factory')->getEditable('mymodule.foo');
+ * 
+ * Individual configuration values can be unset using the clear() function,
+ * which is also chainable.
+ * @code
+ * $config = \Drupal::service('config.factory')->getEditable('system.performance');
+ * $config->clear('cache.page.max_age')->save();
+ * $page_cache_data = $config->get('cache.page');
  * @endcode
+ * In this example $page_cache_data would return an array with one key -
+ * 'enabled' - because 'max_age' was unset. Whole configuration sets can be
+ * removed using the delete() function.
  *
  * @section sec_entity Configuration entities
  * In contrast to the simple configuration settings described in the previous