The bug appears similar to one involving FamilySearch. Go to the wiki, at wiki.familysearch.org and first set your browser to 100 percent if not already set there. Then try to reduce that to any setting below that, and you'll see some elements of the page go down to the bottom of it.
So try the same thing with the Study Notebook, if it appears normally at 100 percent, but not at a reduced size, then that may be the issue. It's a known issue at FamilySearch and they've been dealing with it for a few months but they haven't even been able to figure out how to prevent it yet, there are some other header/footer issues FamilySearch is having as well that also could be affecting Study Notebook on top of that.