Hi Mark,
Here is the jquery syntax that you can use...
$("input[name='QR~QID2#2~TEXT']").attr('maxlength',8);
Let me know if it doesn't work. Share direct link of question to better understand and I can help.
All the best with your project!

Sorry cbhavsar I'm not sure where to add that syntax. Are you able to write it out in full for me?

Qualtrics.SurveyEngine.addOnReady(function()
{
jQuery("input[name='QR~QID2#2~TEXT']").each(function () {
  jQuery(this).on("inputuname='QR~QID2#2~TEXT']").attr('maxlength',8);
});
});

Here you go...
Qualtrics.SurveyEngine.addOnReady(function()
{
  jQuery("inputuname='QR~QID2#2~TEXT']").attr('maxlength',8);
});

Thank you!