assuming the last guest left at 6:32pm thus that'll be the duration of the party.
from 4:30 to 5pm is only 30 mins, from 5 to 6:32 is 1hr and 32 mins, now let's add the 30 mins from before, 1hr + 32 + 30, that's 1hr and 62 minutes, or namely 2hrs and 2 minutes.