Both serial ports (LL serial 0 and HL serial 0) have the same physical interface. To communicate with the vehicle using the XBee link or the USB Cable Adapter (AscTec USB - AutoPilot), please connect to the correct virtual comport using the following connection settings:
Flow control: "Hardware" for XBee, "None" for USB cable adapter
Databits: 8, 1 startbit, 1 stopbit, no parity
Max. current: 300mA
I don't understand what "flow control" for Xbee means.
This means, that the XBee automatically uses hardware flow control (CTS pin) whereas the USB adapter does not (it ties the CTS pin to GND).
For your daily use, this fact should not be of any importance, it is just stated for completeness in the wiki.