@Override
    public String toString() {
        return String.format("Request: %d/%d, Response: %d/%d",
                requestBytesTransferred, requestContentLength,
                responseBytesTransferred, responseContentLength);
    }
Returns the number of bytes that have been transferred in the response.
aws-java-sdk-core/src/main/java/com/amazonaws/event/request/ProgressSupport.java