“Food manufacturers are allowed to list amounts of trans fat with less than 0.5 gram (1/2 g) as 0 (zero) on the Nutrition Facts panel. As a result, consumers may see a few products that list 0 gram trans fat on the label, while the ingredient list will have “shortening” or “partially hydrogenated vegetable oil” on it. This means the food contains very small amounts (less than 0.5 g) of trans fat per serving.”
this is why (one reason anyway) that you get crackhead portions on food containers, 1 12oz can of pop is usually considered 2 servings on the label but for 99% of the human race its 1.
snackwell cookies have some devils food chocolate cookies with a similar listing, 0 fat but iirc the serving size is one cookie.