I have tried to perform the calibration today as per the instructions.

I reckon that the car sits too low as everytime when I cycle between Normal -> Off Road -> Normal I get "Suspension in extended mode...", hit lower once-twice more and then finally it gets to Normal.

Anyway, I've taken 2 sets of separate measurements and the values are slightly different. I've taken them in two car parks (Asda and Waitrose) and the surface seemed flat and level:

Take 1:
- current calibration: o/s/f 209mm, n/s/f 199mm, o/s/r 199mm, n/s/r 183mm
- current height: o/s/f 1mm, n/s/f -3mm, o/s/r 4mm, n/s/r 9mm
- ruler measurements: o/s/f 465mm, n/s/f 470mm, o/s/r 465mm, n/s/r 484mm

Take 2
- current calibration: o/s/f 209mm, n/s/f 199mm, o/s/r 199mm, n/s/r 183mm
- current height: o/s/f 4mm, n/s/f 1mm, o/s/r 5mm, n/s/r 4mm
- ruler measurements: o/s/f 468mm, n/s/f 474, o/s/r 468, n/s/r 474mm

Does the above look alright? Also, how to ensure that the ruler measurements are accurate, i.e. is 1-2mm important when taking the reading with the tape?