Overpayments are tracked in Striive to help you make refunds when necessary.
The most likely reason you will have an overpayment is if you end a session pack early and set a final price that is less than the amount the client(s) have already paid. This will result in a refund being due, which appears as an overpayment on your dashboard:
To correct an overpayment, simply go to the session pack and post a refund payment to bring the balance to zero. When doing this you should also ensure you have made the corresponding payment to the client.
