Hello Tracy,
Once you pass the Final Exam of the Agile PrepCast, the certificate will show 37 PDUs. If you use this for your ACP Exam, you have more than enough to present to PMI for they only need 21 PDUs, thus they will accept it.
In our website, we advertise that the Agile PrepCast will satisfy the 21 PDUs needed for your ACP Exam, but that doesn't mean that you will get 21 PDUs only. The total PDUs that you will get from the Agile PrepCast is 37 PDUs.