The RFC5246 states the following:
The encrypted data length (TLSCiphertext.length) is one more than the sum of SecurityParameters.block_length, TLSCompressed.length, SecurityParameters.mac_length, and padding_length. Example: If the block length is 8 bytes, the content length (TLSCompressed.length) is 61 bytes, and the MAC length is 20 bytes, then the length before padding is 82 bytes
What is the extra byte and what should it be? Also, the maths doesn't quite seem to add up. The first section says the length is the sum of the block length, the contenct length, the MAC length and the padding length. So why in the example is the 8 byte block length ignored in the calculation?