Observations
If the value is A, pins 2 and 5 are set to HIGH to provide a forward movmement in both the motors. If the value is T, pins 3 and 4 are sent a HIGH to provide a backwards movement to the motors. If the character is G, only pin 5 is sent a HIGH to make the right motor turn forward causing the robot to go left. If the character is C, pin 2 is provided a HIGH to make the left motor move forward which results in the robot moving the right.
We observed that the pins which are required to be turn HIGH and LOW are relative to how one positioned their motor and wired their motors. If the motor is wired differently, different pins would need to be turned HIGH to provide the proper desired motion. While programming, it required some trial and error to figure out the correct pins to turn HIGH to power the motor in the right direction.