Overview
The reserve capture flow is used to handle payments using dual message communication. The funds are first reserved through a call to the Payment Integrator hosted reserveFunds method. If this method synchronously returns SUCCESS it means that the funds are reserved and can be captured or released. This step is commonly known as an performing an Auth or Authorization.
Capture funds reservation
The funds can be captured by a call to asynchronousCaptureFundsReservation. This will start the process of moving the funds into Google's account. 
Cancel funds reservation
Alternatively, the reservation of funds can be canceled with a call to asynchronousCancelFundsReservation. This frees the hold on the funds. If a reservation is canceled there is no money movement. Reservations are automatically canceled after a fixed period of time, typically seven days. 
Acquirer reference number
If the funds are captured, a ARN (Acquirer Reference Number) is generated. That value is usually not known to the Payment Integrator until a few days later. Once the value is known, the Payment Integrator must call the Google hosted setAcquirerReferenceNumberForCaptureNotification
Subsequent operations
If the funds are captured, the payment may be refunded by Google with a call to the Payment Integrator hosted asynchronousRefund method. Alternatively, the user or issuing bank can start the chargeback process which is handled through the dispute flow.