This option will allow you to limit the number of times that the Workflow is processed.
You may be monitoring the HR Record for changes to the employees address in order to notify the pension company of any amendments, in which case you’d be monitoring changes to any of the 5 address fields. If someone changes addresses, it’s likely that most or all of the 5 fields would change, potentially triggering the Workflow up to 5 times. In this case you would limit the number of times that the Workflow was processed by setting Exclude If to Already Done Today.
You may have a Workflow Process that runs daily that emails Line Managers to inform them when Doctors Certificates are required following employees absence. You won’t want the same Line Manager to be emailed on a daily basis, rather a reminder sent in a week if the Doctors Certificate was still outstanding. n this case you would limit the number of times that the Workflow was processed by setting Exclude If to Already Done This Week.