diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericFormatterBase.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericFormatterBase.php
index de1776b..0c8cfeb 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericFormatterBase.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldFormatter/NumericFormatterBase.php
@@ -96,6 +96,14 @@ public function settingsForm(array $form, FormStateInterface $form_state) {
    * Form API callback. Sets the value for format_plural_string.
    *
    * This method is assigned as a #after_build in settingsForm() method.
+   *
+   * @param array $element
+   *   Textfield elements where the plural format should be set.
+   * @param \Drupal\Core\Form\FormStateInterface $form_state
+   *   The current state of the form.
+   *
+   * @return array
+   *   Textfield elements with plural string set.
    */
   public static function formatPluralValuesAfterBuild($element, FormStateInterface $form_state) {
     // The 'format_plural_values' element is a list of textfields, but we want