Oh damn! That's a Pathfinder 1 book! - I'll see what I can do about refunding you.
Edit: The request has been sent to the itch.io staff for it to be refunded, but I'm afraid I don't know how long it'll take for it to be processed.
I'm really sorry about this, but I hope you've enjoyed the other 5e books that I can see you've picked up. :)