Lightbox container

I am using Lightbox to display a HTML page. It works great, but when I open the popup,there is an empty white space at the bottom of the Lightbox (see attached image). I would prefer my text to take up the entirety of the Lightbox.

I have tried adjust the size, but it it doesn't seem to have an effect. Would anyone have an idea on solving this issue?

<p><a href="/sites/default/files/Affiliate.html" rel="lightframe">Affiliate Form Agreement</a></p>