This is important because the KMS host computer uses the CMID to determine the number of unique clients.

Freezes the grace timer until either an Office application is run, or the ospp.vbs script is run.

Rearming does the following important tasks: If you do not rearm, users might see notification dialog boxes at the time that the image is deployed, instead of 25 days after deployment. If you want to deploy a volume licensed version of Office, Project, or Visio, as part of an operating system image, you must rearm your Office installation before you capture the image. If activation is successful, users don't see notifications to activate.

The 25-day grace period gives ample time for a KMS host computer to be found and activation to succeed. There is a 25-day grace period from the time of installation of Key Management Service (KMS) clients before notifications to activate are displayed to the user. Applies to: Volume licensed versions of Office LTSC 2021, Office 2019, and Office 2016 (including Project and Visio)

Office 2016 cmd key