How can I get my lightbox newsletter form to adjust to the correct width on mobile?

The lightbox appears after 15 seconds. Far too wide on mobile devices. I've tried changing the width to 100% but that didn't work. I've also tried ticking the box for making the form 'responsive'.

This is the script:

<script src="https://form.jotformeu.com/static/feedback2.js?3.3.REV" type="text/javascript">

      var JFL_62002097936354 = new JotformFeedback({

        formId: '62002097936354',

        base: 'https://form.jotformeu.com/',

        windowTitle: 'Like to hear about every new post? (I won t send you ****).',

        background: '#b4e4b8',

        fontColor: '#FFFFFF',

        type: '1',

        height: 500,

        width: 700,

        openOnLoad: false

      });

    </script>

      <a id="lightboxdelay" class="btn lightbox-62002097936354" style="margin-top: 16px;display:none;">

        Like to hear about every new post? (I won't send you ****).

      </a>

<script language="JavaScript">

var delayseconds = 15;

    function pause() {

    myTimer = setTimeout('whatToDo()', delayseconds * 1000)

    }

   function whatToDo() {

document.getElementById('lightboxdelay').click();

    }

window.onload = pause;

</script>

Any help much appreciated!

Unfortunately, the Lightbox embed code is not (yet) mobile responsive. However, I do have a temporary workaround that you can use. You can refer to this link for the custom script that I have made: http://www.jotform.com/answers/755277-How-to-make-Lightbox-embed-code-mobile-responsive 

I hope that helps.