BE Simple Core Pack: Includes all features and options of Backup Exec, plus 5 Instances which can be used for any physical, virtual or 10 M365 users instance (base requirement per site).
BE Simple Add On: Includes 1 Instance (requires BE Simple Core Pack).
An Instance is defined as a simple compute instance (e.g., a virtual machine in a cloud environment or physical host in a data center) or 10 M365 users.