Email Deliverability Tool

I am trying to find information about the email derivability tool and how the billable events work. I have seen the documentation on it but the main question I wanted to clarify is if I send Email 1 and review it, take into account the feedback, make edits and resend Email 1 to the tool does that could as 1 billable event or 2? I think it counts as 2 events, but I can’t seem to find a confirmation of this.
 
Any insight will be helpful. I have visited both he Tool’s site and gone thoroughly through the community