Quiz Embedding Issues

Hi there.
I’m trying to embed a Sporcle quiz into a post using the HTML from the embed button on their site. It looks fine in the preview within the editing page but once I go to the full preview page (or publish it) the right hand edge is cut off. I’ve tried manually changing the width in the HTML but it doesn’t change the result when I go any narrower than their narrowest standard setting. I also removed the sidebar widget but then the whole post went further across the page and still had the same issue. Any ideas why this is happening? Thanks! (And sorry if any of this is ignorant, I’m brand new..)