I'm having issues programming our team's drive motors, and I am programming them on asumptions.

I am assuming that the following is true:
joystick left on x-axis = value of 126 to 0
joystick right on x-axis = value of 128 to 255
joystick down on y-axis = 126 to 0
joystick up on y-axis = 128 to 255
Can someone confirm that my assumptions are true, or that their false? Thanks in advance.