Choosing a workflow trigger
Use triggers to initiate an automated workflow.
When you use a filter to identify the people, apps or tasks to which the workflow applies, the number of current matches is displayed. To prevent runs from being created for the current matches when the workflow is enabled, select Exclude existing matches on first run; a run will only be triggered when a new match is identified.
If you make changes to the filter for an existing workflow, the number of people, apps or tasks that match the new filter criteria is displayed, followed by the number of new matches. If you save the changes and enable the workflow, a run will be created for each of these new matches. To prevent runs from being created for these new matches when the workflow is enabled, select Exclude existing matches on first run.