On an ABS (absolute) digital scale, you have a zero point and an ABS (or as I like to call it an auxiliary) zero. They can be set to two different points, and you can switch between each zero point without loosing both. It's stored in the readouts memory and removing the battery will reset both.
This means in your case, you can have your normal zero with the micrometer faces touching then swap over to your ABS zero to set it to a part length for comparing a batch of pieces, then back to your true zero all without resetting anything. The ABS button swaps between your two zero origin points. In a nutshell you have two zero points that can be reset independently. Hope this helps