Drip sent random sample emails

Hi all,

I am very new to Marketo and I have a bit of an urgent request.

I am setting up a 7day drip campaign (think that is the correct terminology) to a list of people.

This list I am randomly sampling to select the a random batch of say 500 - 600 people.

Once they have sent the 600 that day I have set up a wait and will send the next 600 people the same email. This happens until everyone in the list has been sent the email (will last 7 days).

I have set this up but so far all that has happened in the first people who received it got it sent to them again a few days later and no new people have been sent this.

This is the set up I have done. I have set up the list and the 7 days of lists afterwards. I have put in an interval send too.

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This one has all of the lists and days in it and is scheduled.

I am really stuck on what the issue is and why it is not working.

Thanks all.

Storm