If so, the question now arises, 50 of what is John in possession of?
You cannot say that John is in possession of anything other than NGN. Why? Because according to subject verb concord in English, John is said to have the same item as the first person in the statement, Lizzy, has. It is like saying, "Zestimony has 10 cars, and Olujay has just 3." Meaning, "Zestimony has just 10 cars, and Olujay has just 3 cars." So, automatically, John has 50 NGN, but "NGN" was clearly removed to present ambiguity.
In my opinion, the answer would be "unknown" or "undefined." This is because the question is in reference to the present and not the past nor the future. And from the statement we have, only John's present state was given, and not the other two. Since we do not know how much Lizzy and Fifi have currently, we cannot say who has "more." Hence, the answer would be "unknown."