You should be able to see a very small amount of your own vehicle, but that is not required. Mainly, you need to be able to see the lane to the left of you... The rest you will adjust to over time.
From the B pillar backwards on the vehicle should be visible within the left mirror. This way, you may approximate the distance between you and another vehicle if you are attempting to change lanes.
mine is set to see just the rear panel of the car and most of the lane behind and to the side of my car, but at night this is a problem when the headlights hit the mirror