So what they do is, let's say you take two people who meet up, and they take the number of days those two people spent together, and then they estimate how many hours were in those days -- how many hours did those two people spend together?
Sie machen das so: Zwei Menschen treffen sich. Dann nehmen sie  die gemeinsam verbrachten Tage und schätzen die Stunden: Wie viele Stunden hatten die zwei Menschen zusammen?