Serving size and Nutrients

MyDynamicJourney

I noticed when selecting a food that different countries have different numbers. Got me thinking. What is considered a serving? Do we all think a serving is just that or do we all think of a serving differently. Calories, Fat, Carbs, Protein, Sugar etc. will be significantly different if a serving is not universally the same. Maybe this is just different from Fast Food Restaurants and not our own homemade food. Thoughts? Even more important to eat clean and prepare our own food. Any one noticed this?