The alias is meant to help you identifying the self hosted runtimes in the cloud metering console.
If you give the same alias to these 4 runtimes, you’ll see consolidated metering data for these 4 runtimes.
If you give these runtimes distinct aliases, then you’ll display metering data for each runtime.
If these 4 runtimes are part of the same cluster and they have the same role, you should give them the same alias.
If they have distinct roles (for instance 2 runtimes for Active Transfer and two for Integration), then you could give them distinct aliases.