In other words (7) should be interpreted with the object NP (its appropriate extension) taking wide scope over the subject NP.This fact can be represented precisely with the help of the notion of the case extension.
the basic meaning (which should be completed by some existential presuppositions) of (7) is given in (8):(8) (NO TWO LANGUAGES) (SOME AND NOT EVERY STUDENT) nom KNOW What (7) basically means is that there are no (two) languages which are known by some but not by all students and not that for every student there are two languages such that he/she knows them.