A factory at a low elevation ships bags of popcorn to cities at high elevations. Why does the factory manager need to monitor the amount of air in each bag

A factory at a low elevation ships bags of popcorn to cities at high elevations. The factory manager need to monitor the amount of air in each bag because when the bags of popcorn are delivered into high elevation cities, it will shrink due to the high pressure exerted by the surroundings towards the bag. As the elevation increases, the pressure surrounding it also increases.