Great question, sorry for the confusion.
For the Quiz ONLY...one serving = 2 Tbsp. This is simply to ensure you are adding in the colors you need. Remember, this is a minimum so add more if you'd like and it fits into the cup.
When building a Blast on your own, then you can use the servings sizes we most often use from the USDA. 1 cup leafy greens, 1/2 cup fruit or 3/4-1 cup berries, 1/2 cup or more of veggies, etc.