Digital Odometer Question

[Necronommicon]

Where is the info on a digital OD. stored? Is it in the gauge itself or is it in the ECU? I have a gauge that doesn't work right in another car and I have a spare that works perfectly, I just don't want to swap them out because the good gauge shows higher miles. I'm afraid I will show the wrong amount, so help please?

 

[2000SE]

I've always thought that the miles are ECU stored. Don't quote me on it though.