It would be an awesome app if the customer service was not so bloody awful. They're out to get your money by any means possible with no care in the world for your concerns over their very shady practices.
Edit following developer response: I was not offered any refund for the impressions despite my requests.
Sorry for the misunderstanding that you might have during our support. We clarified in the email how we count impressions and it has been the way Sale Kit been working. We understand that you might not find this suitable for you, we agree that we can refund to you for the impressions count. But if you still find this solution doesn't satisfy your concern, we can discuss further via email to find out the best solution for you.
Have a nice day.