Science Homework Help

I’m studying for my Environmental Science class and don’t understand how to answer this. Can you help me study?

In science class you learn that there are approximately 1.3 x 107 km3—or 1.3 x 1019 L—of fresh, liquid water on Earth. You also learn that there are approximately 6.7 billion people living on Earth. According to a classmate, this works out to approximately 1.94 x 109 L of liquid fresh water for each person on Earth. Your classmate concludes that reports of water shortages in various parts of the world must be exaggerated.  Why is this an invalid conclusion?