A normal cam is ground with the intake valve opening BTDC and the exhaust valve closing ATDC the same number of degrees. Look at the Lunati cam events above, and you'll see that the intake opens at 15°BTCD, and the exhaust closes 12°ATDC. I'm assuming there's a half degree rounding error, and I think some of the events are in cam degrees, and others are in crank degrees, just to make everything even more confusing, but you can see that the events are moved forward of where they would be if they were both the same number of degrees before and after TDC. The numbers they publish are what you should measure if you degree your cam in and everything is within spec. My speculation on why they do this I feel are purely for marketing reasons--putting a bandaid on a poorly designed cam, and this isn't done because the cam companies don't know what they are doing, but because hot rodders don't know what they are doing, and the cam companies don't want their products getting bad mouthed because someone purchased a cam too big for the application. They want a big cam because it's cool, get one that's too big, has a soggy bottom end, so they advance it to give a little more bottom end. If you know what your motor wants, you can surely take the advance out.