Expenses that count towards 4K required for education credits

I'm looking to enter my books and materials that I paid for out of pocket. I use the 529 plan to pay for her tuition. I use my own cash to pay for her books. However TurboTax seems to indicate that I cannot put books and materials as an education expense unless you bought them directly from the college? That sounds odd to me? So if I bought the books on Amazon that doesn't count towards the 4K required to get the full 2500? Where would I enter these?