We prevent the cleanup process when the number of files considered for cleanup is more than a certain percentage of the total number of files in your backup set. This is done to avoid inadvertent data loss in case of an unexpected event on your computer. For 'Cleanup Now', this percentage is set to 25% by default.

For 'Periodic Cleanup', we give you more control by allowing you to set the frequency as well as the percentage of files to be considered. The frequency can be set to anything between 10 and 30 days and percentage to anything between 5 and 25%.

For example: If frequency is set to 20, your cleanup will be performed after every 20 days, If percentage is set to 10% and if the number of files for cleanup are more than 10% of the total number of files in your backup set, then the cleanup will not occur.