functions.php

<?php

/**
 * Shorter title for About breadcrumb
 *
 */
function be_shorter_title_for_about_breadcrumb( $crumb ) {
  $long_title = 'This is the long about title';
  $short_title = 'About';
  
  return str_replace( $long_title, $short_title, $crumb );
}
add_filter( 'genesis_page_crumb', 'be_shorter_title_for_about_breadcrumb' );