How are you setting the element selector? If the element could not be found, the plugin will fall back to the percentage you set so it could be that that's what happening.
Just to make sure: given the following piece of HTML, the element selector would be
As for the styling issue, this sounds like a theme issue. The plugin tries to blend in with your theme and doesn't come with it's own styling rules.
I took a quick look at your theme stylesheet and it looks like most heading / list related styling rules are applied to everything inside the
Not sure what the multiple boxes could be about. Is just multiple instances of one box (same content) or does it have other content in it?