__________is formulated to meet the nutritional levels established by the AAFCO (Association of American Feed Control Officials) Dog Food Nutrient Profiles for all life stages.

It means that they have not done actual feeding tests on actual dogs with their product, but are using the amount of protein, calcium, etc. established by tests conducted by others using other food.

It means it was never fed to dogs to see if it works, it was formulated in the lab and your dog is the guinea pig.

I personally will not feed a food that wasn't actually fed to dogs in a feeding trial.

GOOD LINK ON THIS

I'm not sure feeding trials are much of a guarantee either. The feeding trials detect only severe inadequacies and acute toxicities because of the limited duration. Some trials are as short as six weeks in duration.
Case in point, the cats who were fed foods with low taurine levels all passed the feeding trials or were excluded due to genetic cardiomyopathy. Only when the cats began eating the safe and balanced foods in the real world did they begin dropping dead from cardiomyopathy by the thousands.
The same thing is beginning to happen with diabetes and who knows what else...the feeding trials are simply not long enough to show that the dog will thrive and just no survive on the foods. It can take months or even years for nutritional inadequacies to come to the surface.
It's a shot in the dark really, so choose your poison