What is a System ID and where do I find it?
 

A System ID is a number assigned to an Avid product and can be used to identify the licenses associated with that product, obtain support, etc. It can be especially useful for customers with multiple products to be able to identify which licenses belong to a specific Software Updates Plan or Subscription.

System IDs can be found listed with each product in my.avid.com/products and in Avid Link.
How do I find my System ID for Pro Tools?

The System ID associated with an iLok license can be seen in the "Publisher License ID" column in iLok License Manager.
How to Show System ID in iLok License Manager

See How do I find my System ID for my AVID products for links to other products.