Supposed Behaviour for the values of ReportAction Attribute

Yes, that is the expected behavior. Because a Redfish Service is expected to be implemented on devices with limited memory, the "MaxReports" property allows the service to indicate that limited memory may be available for storage of metric reports. (Note that a service implementation with ample local storage could set this number to an arbitrary large number, like 10000) In addition, a "new" metric report may replace an older one if the "max" has been reached, so this can still result in new data being stored.

But since generating a Redfish Event doesn't consume local storage resources (on the service end), there is no reason to limit the number of events that can be produced.

Jeff