HazardsMind:
I was under the impression you had a 240x320 screen, But you have a 240x400 screen. So instead of subtracting 320, you need to subtract 400.
That mean ...
myGLCD.printNumI(x-400, CENTER, 0); //X axis
I Test with
myGLCD.printNumI(x-400, CENTER, 0); //X axis
and
myGLCD.printNumI(400-x, CENTER, 0); //X axis
not better.