diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index f20d0e4..ba18dc7 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -47,9 +47,9 @@ sequence:
   label: Sequence
   class: '\Drupal\Core\Config\Schema\Sequence'
   definition_class: '\Drupal\Core\TypedData\ListDataDefinition'
-  
+
 # Simple extended data types:
- 
+
 # Human readable string that must be plain text and editable with a text field.
 label:
   type: string
@@ -112,7 +112,6 @@ filter:
     settings:
       type: filter_settings.[%parent.id]
 
-
 # System action configuration base.
 action_configuration_default:
   type: sequence
diff --git a/core/lib/Drupal/Core/Config/Schema/Sequence.php b/core/lib/Drupal/Core/Config/Schema/Sequence.php
index ed82d74..e5b6a35 100644
--- a/core/lib/Drupal/Core/Config/Schema/Sequence.php
+++ b/core/lib/Drupal/Core/Config/Schema/Sequence.php
@@ -25,7 +25,10 @@ class Sequence extends ArrayElement implements ListInterface {
    * Overrides ArrayElement::parse()
    */
   protected function parse() {
-    // Get the generic definition and reprocess it for all items.
+    // Creates a new data definition object for each item from the generic type
+    // definition array and actual configuration data for that item. Type
+    // definitions may contain variables to be replaced and those depend on
+    // each item's data.
     $definition = isset($this->definition['sequence'][0]) ? $this->definition['sequence'][0] : array();
     $elements = array();
     foreach ($this->value as $key => $value) {