What happens if I miss my check-in time at the apple store

So I just pre ordered an iPhone XS Max for pickup at Apple Hornsby. I selected a check-in time of 3:00-3:30 but what will happen if I'm late for this check-in time. if I'm just a few minutes late will they just hold it for me? What if I'm an hour and a half late will they sell it to someone else and then I'll have to wait for them to get more stock? Basically why will happen?