This setting controls how much backup history is retained on the SQL Server instance after the data has been collected by the RockSolid monitoring processes.
In general, as history information is centralised into the RockSolid repository off the SQL Server instance it is good practice to keep the amount of history data retained on the instance to a minimum. This ensures that the maximum amount of space is available to user databases rather than being consumed by system historical data.
If you enable this option you must also specify the number of days backup history to retain. RockSolid will automatically purge any backup history data older than this number of days from the msdb database. This purge will occur on an ongoing basis as part of the monitoring process.
This setting can be overridden at the database level, see here for more information.