I think it takes in to consideration things like humidty, temperature, and altitude. So, if you dyno on a day with 90 degree temps you can get a more true reading on the cars power.
STD, or Standard correction factor. The Standard correction factor corrects the dyno numbers to the international scientific standard conditions of 59° F, 29.92" Hg barometric pressure, and 0% humidity. Since cooler air and higher air pressure both result in more air molecules entering the engine, an engine will produce more power under STD conditions than under SAE conditions.
SAE (Society of Automotive Engineers) correction factor. The SAE correction factor tells you what the power output would be if the temperature were 77°F, the barometric pressure 29.23" Hg, and 0% humidity. As such, the SAE correction factor is conservative compared to the STD (Standard) correction factor, and probably more closely reflects the amount of power will be produced under real-world conditions. For this reason, SAE is currently the most widespread correction factor used by auto manufacturers in rating horsepower and torque output
STD, or Standard correction factor. The Standard correction factor corrects the dyno numbers to the international scientific standard conditions of 59° F, 29.92" Hg barometric pressure, and 0% humidity. Since cooler air and higher air pressure both result in more air molecules entering the engine, an engine will produce more power under STD conditions than under SAE conditions.
SAE (Society of Automotive Engineers) correction factor. The SAE correction factor tells you what the power output would be if the temperature were 77°F, the barometric pressure 29.23" Hg, and 0% humidity. As such, the SAE correction factor is conservative compared to the STD (Standard) correction factor, and probably more closely reflects the amount of power will be produced under real-world conditions. For this reason, SAE is currently the most widespread correction factor used by auto manufacturers in rating horsepower and torque output