<script>
(function() {
  var MAXLEN = 15;

  var waitForInput = setInterval(function() {
    var input = document.querySelector('input[type="text"][placeholder*="Ex"]');

    if (input) {
      input.setAttribute("maxlength", MAXLEN);
      console.log("Maxlength set to", MAXLEN, "on:", input);
      clearInterval(waitForInput);
    }
  }, 200);
})();
</script>