No worries, I can explain.
Say the FIRST order, the $90 Dollar order the OP took on to deliver was from a restaurant that suggested approximate delivery time between 15-20 minutes on the Doordash app. for the customer(s) that ordered it. So the customer being aware of this, timed their delivery accordingly and were anticipating their food to arrive within 15-20 minutes.
I guess Door Dash also allows their delivery team to take on more than one order, granted the employee sticks to that 15-20 minute timeline. Seems like the OP had the right idea, but I guess DD does not strictly monitor time, and depend on their delivery guys to monitor their own time, while still allowing them to make more than one delivery at a time.
So I guess what I am trying to constructively criticize the OP here for is, to keep his eye on that timer, and make sure he honors that delivery time window, before taking on a second order.
Having said this, I admit it's not the most ideal, picture perfect delivery service, but it also seems to be 100% optional and not mandated, so I guess that option is left on the deliverer's responsibility to take on or not.
Also, I am not sure every restaurant can afford to have their own personal delivery service.