"C" is Displayed in the Compass Window
WARNING: This page is about a different car, the 2004 Infiniti Q45. However, it is still accessible from the selected car via links, so may be relevant.
The compass needs to be calibrated. Drive the vehicle in 3 circles at 8 km/h (5 MPH) or less until the display reads a direction. You can also calibrate the compass by driving your vehicle on your everyday routine. The compass will be calibrated once it has tracked 3 complete circles.