Each of your physical Proxmox VE servers will need a subscription that corresponds to the number of CPU sockets in that server (1 CPU, 2 CPU, or 4 CPU).
Each subscription key is then bound to the unique "Server ID" of your server.
For example:
If you have 4 x physical servers with 1 socket each, you'll need to order 4 x subscriptions for 1 CPU/year (and not: 1 subscription for 4 CPUs/year).
