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[Description] When used with Automation: Subscriber has triggered an automation workflow and received at least one email. This includes subscribers who have started and completed the workflow. When used with SurveyMonkey: Subscriber has started the SurveyMonkey survey you select. This includes subscribers who have started and completed the survey. [Operator] 
has started
All the Segmenting Options | MailChimp.com: KB Article
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