I'm trying to self-learn the AES128 algorithm and ran into a snag while following these slides I found online: https://kavaliro.com/wp-content/uploads/2014/03/AES.pdf
For the sixth round in the example given, during the Add Roundkey step, the third word of the matrix after MixColumns (F0) is xor'd with the third word of the 6th roundkey (B7). This apparently results in (77) which doesn't correlate with my calculation of 47. However, the process seems to proceed with this error and still gets the right ciphertext in the end(I put the ciphertext through an online decoder and got the original plaintext back).
I'm very confused as to what I am missing here?