Do quality adjectives have a standard?
From Googling Nutritional Claims Excellent:

YES! These terms are highly regulated in the United States.

In the US, the FDA sets the following standards for food products:


  
  "High," "Rich In," or "Excellent Source Of" - Contains 20% or more of the DV per RACC. May be used on meals or main dishes to indicate that the product contains a food that meets the definition, but may not be used to describe the meal.
  "Good Source," "Contains," or "Provides" - 10%-19% of the DV per RACC. These terms may be used on meals or main dishes to indicate that the product contains a food that meets the definition but may not be used to describe the meal.
  "More," "Fortified," "Enriched," "Added," "Extra," or "Plus" - 10% or more of the DV per RACC than an appropriate reference food. May only be used for vitamins, minerals, protein, dietary fiber, and potassium.
  


Note: DV = Daily Value, RACC = Reference Amount Customarily Consumed

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