The key to Burp Suite Enterprise Edition's extreme scalability is the pool of agents:

Agents can be installed on indefinitely many computers, including the main Enterprise server itself. Each agent computer is configured with an agent count. This is the maximum number of logical agents that can run on that computer. Each logical agent can be occupied carrying out a single scan at any time. So if you configure an agent count of 5, then up to 5 scans might be run in parallel on that computer.

You can click into an individual agent to see more details, including its configuration, status, and the scans that the agent has performed:

Burp Suite Enterprise Edition is licensed for a specific number of agents, and the number of concurrent scans that can be performed will be limited to the number of agents in your license. We will describe licensing and pricing in more detail towards the end of this month.