When creating a booking via Impala Booking, the room seller needs to charge the guest the rate amount of the booking prior to making this booking to Impala.
When setting up your production API key, you will have entered your business credit card and this will be used to take payment for the booking. Once you have made a transaction, Impala will charge your card immediately and this will be the amount the guests pays minus the seller commission percentage (the amount you keep for selling the room). Impala will then manage the payment to the hotel for the booking.