Did it take less than 2 hours to create the booth, the signs, and perform the services? Unlikely.
What, you're saying that a team of college students, on a college campus, which presumably has a fully stocked stationery store within five minutes' walk, can't throw up some hand-scrawled signs in less than (say) 15 minutes for under five bucks?
Yeah, they probably had to already have the tire pump and gauge. I presume that "what do we have in our closets" was an important part of the process of choosing this business plan. ;) And I don't seem to recall anything in the "constraints" about not being allowed to beg or borrow anything, nor any rules about not being allowed to use stuff you already own. This isn't accounting class.
did they make the reservations at 6pm and then sell them before 8pm?
Why not? Remember: They're doing this in parallel, using multiple team members and multiple restaurants. And, given the anecdote ("this works better for restaurants that hand out little buzzers") we're not talking about the sort of reservation that needs to be obtained hours in advance. We're talking about people paying for the privilege of jumping the line and turning a 40-minute wait into a 4-minute wait. You can get through quite a few cycles of that in two hours.