I believe the stored target heights (especially on the front) need to be withing 2 bits of each other - as when you come to a stop, it briefly opens both front valves to equalize the pressure between the front air springs. (I'm guessing to try to make sure the headlights are level and not shining randomly off).
If you have target heights more that a couple of bits out then you might see the 'target heights incorrect' message - or if they are outside the expected range for that particular height.
As to the height it actually reports as sitting at - well, that might be a bit off from the 'target', but again especially on the fronts, they should be withing a couple of points of each other.
Hope this helps.