This option controls how much historical job execution history data is retained within the central RockSolid repository. This will affect how much history is available within the RockSolid UI and reports when reporting on job execution history.
Once historical data becomes outside the bounds specified, this will be automatically purged from the RockSolid repository without further confirmation.
This option does not affect the amount of job execution history retained on the target SQL Server instance itself. To change this setting see here.