The most common cause I've seen of this is people buying third-party PDFs (which aren't covered by Pathfinder Advantage), especially when they don't realize they're third-party (e.g. the Pathfinder Paper Minis, which are produced under license by artists working in a third-party capacity.)
However, if this wasn't the case, please ignore me! :)
It looks like the system had some trouble with these. I have given things a poke, and refunded the difference to your original payment method.
If we can help with anything else, please let us know.
Thanks!
Sharaya