Just installed your stats a day ago and found strange behavior of shortcode (and similar php functions) in case I need to display visits or visitors for 'today'.
Both shortcode and wp_statistics_visitor(time) + wp_statistics_visit(time) giving me different numbers if I'm on my site root or any other post/page. When I'm on the root, numbers seems to be correct, but if I'm going deeper reading any post/page, it displays strange (constant) numbers.
UPD... Semi-resolved: looks like this happens only when I'm logged in. When logged out, numbers are always correct.