Request for Credit Refund Due to Email Waterfall Issue

hi - clay used up way more credits than it was supposed to in an email waterfall. I'm not sure if clay performed the waterfall correctly. I had about 15k credits that got used up and it only got through 600 contacts. I even have a paid Apollo account as my first leg that should cover a majority of the emails without expending credits. can you please refund my credits and tell me what went wrong?