My Mitsubishi Galant started showing "Trip [A]" and also shows different miles? What does that mean?
That is the part of the odometer called the Trip Odometer. There should be a button you can push to cycle through the different settings very near the reading, usually in the dash. You can usually press and hold the button to allow for a reset. Since it shows an [A] on it, you can expect there is probably a second one named [B] (at a minimum). If you cycle through far enough, you'll get back to your regular mileage reading. You probably pressed the button accidentally and caused it to get to the trip reading.