Hi bishop
You are not the only one that has sent things that aren`t allowed. Its not all that easy working out what you can and can`t send!
I looked up the DOC website before I sent blank cards to my pp. It said I could send 10. I sent 8 cards. With envelopes.
But, they meant 10 including the envelopes! So, they were sent back to me.
I have had letters sent back that had little Xmas stickers on the envelopes, cards sent back that were considered "lewd", even tho they were just silly cartoon figures; cards sent back because they were expensive cards, and I had put them in a padded envelope to protect them. I sent books that were not given to my pp because I sent more than 4.

It`s easy to send the 'wrong" thing; and to make it even harder, it varies from state to state!
Its a learning experience!