If you replace your instrument cluster with used, the digital odometer setting will not transfer.(At least that'* what happened on my SSEi). The odometer setting is stored in the cluster, and does not transfer from vehicle to vehicle.
So, if you put in a IC from a salvage yard, you will need to attach an adjustment somewhere that will reflect the difference in the actual vs. displayed mileage. You may be able to get a dealer to reprogram the used IC...but I doubt it. They only seem interested in selling you their own remanufactured version.