Each recipe is for one full serving, however you don't need to drink the whole thing if it's too much. Most people drink a whole cup as a meal replacement. Others cut the recipe in half for a snack or they make the whole recipe and save half to finish later. You can seal the Bast using the cap and store it in the fridge for up to 24 hours.
Follow your hunger and fullness cues - don't stuff yourself. The most important thing is that you are getting in some nutritious foods :)