Howdy! I have a pet that I am trying to increase their Intelligence, but I can't read two of the books in my inventory to them. Is this a bug or am I doing something wrong? Details below.

Link to Pet's page: https://subeta.net/petinfo.php?petid=3658660 (if you need more info idk?) Pet Int: 38 Last book read to them: Book package (they did get 1 AP for it)

If there is more I should provide info-wise let me know. I am just a little frustrated trying to grind their Int right now.

Edit: Ope, I think this is user error. Looks like a previous owner of this pet read them the books I was trying to use already...