premise: More often than not, this chamber has had quite a few empty seats on the day Royal Assent is given, which leads me to conclude that it is something which is not as attractive to senators as proceedings on another day would be and which would allow them to be in attendance in larger numbers.
hypothesis: Senators may sit in the seats in this chamber.
reason: The implication is that the seats are for senators, so when the senators don't attend, there are empty seats. The model missed this inference.