Test the garage door with its current settings to see where the problem lies. The door might reverse prematurely, touch the ground and reverse or fail to open all the way.
Stand on a stepladder to reach the motor head. Locate the limit dials on the left side of the motor, marked with a garage door opening and closing icon.
Turn the dials with a screwdriver: turn the "down" dial counterclockwise if the door does not close or clockwise if it strikes the ground. Turn the "up" dial clockwise if the door fails to open fully but moves at least 5 feet. Each full turn represents 5 inches of travel added or removed.
Test the new settings by opening and closing the door. Make any additional adjustments until the door operates properly. You may need to adjust both dials in some cases.