The phrase "grams protein" refers to the measurement of the amount of protein in food or a product. It tells you how much protein is contained in a specific quantity, usually measured in grams. Full definition
You gain about 1 1/2 grams protein for only 35 calories. (cookinglight.com)
Do this quick check, take the number grams protein in a serving and multiply by 4, that is how many calories should be in a serving. (scoobysworkshop.com)