This is an informational event log message only and should not affect testing.
The message indicates the post test realtime.csv result file(s) will stop writing data x seconds into the configured test and will not be collected for the entire test run.
If you would like to disable this message and stop creation of a limited realtime.csv file go to the Run/Configure tab and set the statistic collection to 'Summary' (summary.csv and run-time stats only).