Change input value on click when there is more than one paragraph
I need to loop through the paragraphs with an .each() like so:

/**
 * @file
 * Javascript behaviors.
 */

(function ($, Drupal) {

  "use strict";

  /**
   * Handle paragraph fields on the node edit form.
   */
  Drupal.behaviors.myBehavior = {

    attach: function (context) {
      $("input[name$='[subform][field_my_number_integer_field][0][value]']").each(function (i) {

        $('input[name="field_my_content_paragraph_field[' + i + '][subform][field_my_number_integer_field][0][value]"]', context).on('click', function () {

          var myNumberFieldValue = $('input[name="field_my_content_paragraph_field[' + i + '][subform][field_my_number_integer_field][0][value]"]').val();
          var myInputTextFieldValue = $('input[name="field_my_content_paragraph_field[' + i + '][subform][field_my_input_text_field][0][value]"]');

          switch (myNumberFieldValue) {
            case '1':
              myInputTextFieldValue.val('A');
              break;
            case '2':
              myInputTextFieldValue.val('B');
              break;
            case '3':
              myInputTextFieldValue.val('C');
              break;
          }
        });
      });
    }
  };

})(jQuery, Drupal);


Which solves the problem.