docs(config): refine cluster configuration

Documentation/configuration.md

@@ -41,9 +41,9 @@ configuration files.
 * `-peer-election-timeout` - The number of milliseconds to wait before the leader is declared unhealthy.
 * `-peer-heartbeat-interval` - The number of milliseconds in between heartbeat requests
 * `-snapshot=false` - Disable log snapshots. Defaults to `true`.
-* `-cluster-active-size` - The number of expected peer-mode instances in the cluster. It is used only when the instance creates a new cluster.
-* `-cluster-remove-delay` - The delay before one node is removed from the cluster since it cannot be connected at all. It is used only when the instance creates a new cluster.
-* `-cluster-sync-interval` - The interval between synchronization for standby-mode instance with the cluster. It is used only when the instance creates a new cluster.
+* `-cluster-active-size` - The expected number of instances participating in the consensus protocol. Only applied if the etcd instance is the first peer in the cluster.
+* `-cluster-remove-delay` - The delay before one node is removed from the cluster since it cannot be connected at all. Only applied if the etcd instance is the first peer in the cluster.
+* `-cluster-sync-interval` - The interval between synchronization for standby-mode instance with the cluster. Only applied if the etcd instance is the first peer in the cluster.
 * `-v` - Enable verbose logging. Defaults to `false`.
 * `-vv` - Enable very verbose logging. Defaults to `false`.
 * `-version` - Print the version and exit.