Starting point: Milestone
The starting point "Milestone" continuously imports profiles that reach a milestone. Profiles that have reached the milestone are searched for and imported every 60 minutes.
Multiple passes are not allowed at this starting point. Each profile can therefore only run through this campaign once.
Under Settings you have to select a "Milestone" and all profiles that reach this milestone will be imported into the campaign afterwards. Only profiles that have reached the milestone before the start of the campaign will be taken into account.