How do you know if the odometer has been tampered with on a mk4 supra

[tayman1975]

I replaced the plastic clear dash speedo cover in my car. I had to unhook the odometer to get at it. I then drove over to the parts store to buy a light to go inside my boost control as well. i came back hooked it all back up and finally didn't realize until today that the odmeter wasn't hooked up on the car while i took it out to the parts store. Does the computer make up the difference and know it has been driven. This is a very bad feature on this car. I just bought it and how the hell do i know if the actual mileage is correct.