Better illustrate the purpose

web/slow-but-fast.php

@@ -1,7 +1,7 @@
 <?php
-header('Cache-Control: s-max-age=1, stale-while-revalidate=20');
+header('Cache-Control: s-max-age=1, stale-while-revalidate=99999999');
 sleep(5);
-print('This is a slow instant test. ' . date('Y-m-d H:i:s'));
+print('This is a slow test with as fresh data as possible. ' . date('Y-m-d H:i:s'));
 ?>
 <p id="js-date"></p>
 <script type="text/javascript">