Are those measuring the same thing? Does 63% Carnot efficiency mean 63% of the efficiency of the ideal Carnot cycle, which is determined by the temperature dif

Are those measuring the same thing? Does 63% Carnot efficiency mean 63% of the efficiency of the ideal Carnot cycle, which is determined by the temperature difference and is always less than 100% of the heat energy extracted from the fuel? Or does it mean the amount of fuel heat that is converted to motion? 63% would be fantastically high, I thought.