Update health server setup instructions in documentation

Author: lchenmsft

articles/batch/create-pool-extensions.md

@@ -226,9 +226,9 @@ If Key Vault extension is configured incorrectly, the compute node might be in a
 
 ## Considerations for Application Health extension
 
-The Batch Node Agent running on the node always starts an HTTP server that returns the health status of the agent. This HTTP server listens on local IP address 127.0.0.1 and port 29879. It always returns a 200 status but with the response body being either healthy or unhealthy. Any other response (or lack thereof) is considered an "unknown" status.
+The Batch Node Agent running on the node always starts an HTTP server that returns the health status of the agent. This HTTP server listens on local IP address 127.0.0.1 and port 29879. It always returns a 200 status but with the response body being either healthy or unhealthy. Any other response (or lack thereof) is considered an "unknown" status. This setup is in line with the guidelines running a http server which provides a "Rich Health State" per the official "Application Health extension" documents.
 
-You can set up your own health server that listens on a different port. Optionally, your health server can query the Batch Node Agent server and combine with your health signal to generate a composite health result.
+If you set up your own health server, please make sure that the HTTP server listens on a different port. And it is suggested that your health server should query the Batch Node Agent server and combine with your health signal to generate a composite health result. Otherwise you might end up with a "healthy" node that doesn't have a Batch Node agent running.
 
 ## Next steps