IMPORTANT: Delivery time is always added to the pick up/dine in/default order ready time.
The system has a set time for pick up or approximately how long it takes to prepare the order (Pick Up or Dine In). Located under "Manage Restaurant" -> "Restaurant Account Information". It's called "Default Order Ready Time"
Delivery Time is set under Delivery Settings (Manage Restaurant -> Delivery Settings)
This makes the actual delivery time: 30 + 20 = 50 Minutes.
Orders for Pick Up or Dine In, see the ready time as 30 Minutes.
In order to adjust delivery time, you can adjust either of the above 2 areas in order to get the desired time.