What is there to be confused about . I followed what was given , it's not the volume I care about it's why was the resister overloaded. It's a ten watt resister. The way the circuit is destined the power for the headphone and the total power goes through that resister but regardless how odd I achieve excess of 10 watts . Now that the headphone is out of the circuit it's fine ice cold . So the headphones were using some serious power .
Just because the resistor got hot doesn't mean it was dissipating more than 10W. Cement wire wound resistors get quite warm at rated load.. burn your finger warm... That's how they are designed.