Android Question BLE Notification on TI Sensor Tag

I've to read the data from TI Sensor Tag. I've enabled the sensor and activated the notification locally using the BLE2 library (manager.writedata and manager.setnotify) but I can't undersatad how to implement the last 3 rows (in red).
Can anyone help me ?

The following code is from TexasInstruments
/*
* This is a self-contained function for turning on the magnetometer
* sensor. It must be called AFTER the onServicesDiscovered callback
* is received.
*/
private static void turnOnMagnetometer(BluetoothGatt bluetoothGatt) {
UUID magnetServiceUuid = UUID.fromString("f000aa30-0451-4000-b000-000000000000");
UUID magnetConfigUuid = UUID.fromString("f000aa32-0451-4000-b000-000000000000");
BluetoothGattService magnetService = bluetoothGatt.getService(magnetServiceUuid);
BluetoothGattCharacteristic config = magnetService.getCharacteristic(magnetConfigUuid);
config.setValue(new byte[]{1}); //NB: the config value is different for the Gyroscope
bluetoothGatt.writeCharacteristic(config);
}
/* The next step is enabling notifications. Enabling notifications is a two-part job, enabling it locally, and enabling it remotely. It can best be explained in code, see the following code snippet.
*/
private static void enableMagnetometerNotifications(BluetoothGatt bluetoothGatt) {
UUID magnetServiceUuid = UUID.fromString("f000aa30-0451-4000-b000-000000000000");
UUID magnetDataUuid = UUID.fromString("f000aa31-0451-4000-b000-000000000000");
UUID CCC = UUID.fromString("00002902-0000-1000-8000-00805f9b34fb");
BluetoothGattService magnetService = bluetoothGatt.getService(magnetServiceUuid);
BluetoothGattCharacteristic magnetDataCharacteristic = magnetService.getCharacteristic(magnetDataUuid);
bluetoothGatt.setCharacteristicNotification(magnetDataCharacteristic, true); //Enabled locally
BluetoothGattDescriptor config = magnetDataCharacteristic.getDescriptor(CCC);
config.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
bluetoothGatt.writeDescriptor(config); //Enabled remotely
}