Anyway. Maybe by "between", they mean "and not equal to"? Probably not, but let's try anyway, just in case:
Gah! Oh well, I only need one footnote. Rather than spend time figuring out what it really wants, I'll change the format, and use a custom mark instead:
1 Note the different capitalisation of the "at" in the dialog box and error message. Sloppy.2
2 Also, note the easy use of footnotes in this post.