What's the math that gets to 3-4 hours? Do the drones usually multiple deliveries in a flight? In my metro I would have assumes that any place is less than 30 m

What's the math that gets to 3-4 hours? Do the drones usually multiple deliveries in a flight? In my metro I would have assumes that any place is less than 30 minutes flight time from a Whole Foods or Walmart for example. How long does the actual safe delivery take? I assume it just lowers the goods and doesn't wait for the customer, right? Edit: The Internet tells me that delivery drones fly at 40-60mp/h which is much faster than I assumed and makes the 3-4 hour window even more surprising to me.