So for the "Flush size (bytes)" and "Flush interval (seconds)" parameters. The default values are a good starting point and should be adjusted based on your needs.
Lower values will make the event server produce many small files with only a few events, which is often not desirable. Larger values will create fewer bigger files, but if the event server crashes, potentially more events are lost.
You can monitor and see how many logs your instances produce and adjust based on your usage of the logs and the frequency you want them.