Popup modal box needs modification to adjust resizing

Hello,

I have a modal box on a website that almost works.  However, it is not resizing properly.  The person who developed the overal modal plugin is using an open source modal javascript in his program.  But he doesn't know how to make the fix in the javascript portion.

It's easier to show the issue than to explain.  So here is a link to a test page with the popup window

Link to page with popup window

And attached is the javascript that needs to be tweaked.

The popup is activated on the website when you click on the top menu "LOGIN - MODAL TEST"

When you click on it you will see one thing which need to be fixed

The height and width need to be the size of the background image, which is 311px wide by 381px tall.

For some reason the box resizes to a smaller dimension.

I don't know much about javascript.  The good thing is the script seems to be very well commented, so a Javascript expert should hopefully know where to make the changes in the attached js file.

Note: I am also including a css file and a php file -- but the developer says the resizing "problem" is controlled by the js file.

Also: You'll the specific CSS for the background image is in the header of the page.  

  <style type="text/css">
#mbCenter {
    background: url("/Images/login_bg.png") no-repeat;
}
</style>

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Note, any fixes can be hard coded -- if that's easier.  The modal is only going to be used for this one purpose.

Thanks for any help!

Rowby
mediaboxAdvBlack21.css
mediabox-ck.php
login-bg.png
mediaboxAdv.js