My 2009 C70 compass in the mirror was consistently 45 degress off. I tried and tried the calibration process from owners manual. I accidently found that if you press the button on the bottom of mirror for 12 seconds a new display toggles between "L" and "A". I switched to "L" and recalibrated and now the compass is correct. I am posting this for others that may also be having problem.
Any one have any idea what this other setting is?