This is an informational message that tells the administrator that the IPS "Block Log" has filled up and in order to add further entries the old entries have to be removed. In the example above, event numbers 31249223 to 31261311 from 22 Feb 2013 14:49 until 22 Feb 2013 15:09 were removed from the log.
Note: The IPS device maintains a historical log file and a current log file for each log. When the current log file reaches the default size (4MB), the log is de-activated and saved as the historical file, and a new log file is started as the current log. If a historical file already exists, that file is deleted. When the log is rolled over, the system generates a message in the Audit log. If you want to save all log data and create a backup, you can configure the system to offload log messages to a remote system log (SYSLOG).