Using a severe filter writes only severe error messages to the event log, but by default and at https://<IP_address>:8082/Eventlog/Statistics the entire unfiltered log is downloaded. The URL is:
This is by design; the unfiltered log contains all the logs regardless of the event log filter in use.
However, the event log filter only sends filtered events via SysLog (for example, sends severe events only if filtered for severe events). The Management Console (Statistics > System > Event Logging) also contains only filtered events.