That’s 20ppm, not 20,000 ppm. https://www.fda.gov/food/nutrition-education-resources-materials/gluten-and-food-labeling
“The rule specifies, among other criteria, that any foods that carry the label “gluten-free,” “no gluten,” “free of gluten,” or “without gluten” must contain less than 20 parts per million (ppm) of gluten.”

Dining and Cooking