I honestly believe that full generations of drivers were taught to adjust our mirrors improperly.
CORRECT:
Lean your body toward the center of the car - adjust the passenger mirror so you barely see the back edge of your car.
Lean your body and touch your head on the driver's window - adjust the driver's mirror so you barely see the back edge of your car.
In VERY LIGHT traffic CAREFULLY test the setup so traffic appears in the side mirror before it disappears from the rearview / so that traffic appears in the window before it disappears from side mirror. Repeat for other side.
Tip: Once correct, you can also lean slightly from side to side as you check the side mirrors to see even more area.