This setting controls when local account data will be automatically cleared from the system and is the number of days from the last time the account last signed in. Pre-mapped accounts that have not been seen are also cleared.
The setting can be from 1 to 365 days and represents the number of complete days that have passed since the date the account last signed in. i.e. does not include the day of the last sign-in in the count. See also: How to modify a local account.