offset doesn't seem to change when to display box

Great plugin! Exactly what I was looking for, except….

I am wanting the box to appear rather soon as a person scrolled down my post. I tried changing the % for Offset to a lower value, but no matter what value I put in, the box seems to appear almost at the same time (almost at the end of the post). I’ve even set it to 10% and 0%, but it waits until at the end.

Is there something I am missing? Thanks,

Tony

http://wordpress.org/plugins/upprev/