Stock 340 dyno tests?

Another little troubling thing I ran across in the early 70's........was reading one of the popular mags...Hot Rod, Popular Hod Rodding, Car Craft, I don't remember

Little box way WAY in the back of the mag

Said, basically, "we sometimes factor the numbers if we think the weather, the driver, the tires, bla bla bla in other words, the chevies sometimes got better numbers out of the sky because "they thought so"