You have conflicting instructions on your website and this one - on yours you say to use single brackets, on this one, double.
Either way, it doesn't work for me. At one point, I got the hover box to come up, but it displayed the entire page instead of just the footnote info. Other times I couldn't get it to work at all.
Nor did it display the number in superscript.
Really wish it worked. Maybe it's a conflict with my theme, but whatever, I'm sad that I couldn't get it to go.