"
Kublai Khan does not necessarily believe everything Marco Polo says when he describes the cities visited on his expeditions,..."
In the view of the meaning of "not necessarily", I interpreted the sentence as;
Kublai Khan believe
the part of everything Marco Polo says when he describes the cities visited on his expeditions
Am I right?
The sentence is quoted from
http://www.ndsu.edu/pubweb/~cinichol/CreativeWriting/323/CalvinoInvisibleCities.htm