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Shown: the total number of times your form was shown to your customers.
Sessions: the number of sessions this form was on.
Completes: the total number of times your form was completed and submitted.
Conversion: the percentage of opens forms that were opened and then submitted.
Closed before complete: the number of customers who opened the form but closed it before submitting the form.
Triggered by passive/proactive/exit: the number of times your form was triggered by a certain action. You can read more about triggers in this article: How can forms be triggered?.
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