Because he (and Flo) keep a running score of the matches. Meaning they give 20 when someone makes the finals, 10 when they make Bronze, etc. It's how they do it and have been doing it for as long as they have been covering Worlds/Olympics.
They also do this with NCAAs. Once they make the semi-finals they get the allocated points for at least 6th place, when they win the semi-finals they get the allocated points for at least 2nd place, etc.
This is all S.O.P.