I understand that you have some questions about the audio connections on the back panel of your Slingbox PRO-HD.
One of the main advantages of the Slingbox PRO-HD is that it allows you to connect up to three devices at the same time. This means that you can use either the analog audio cables (red and white) or the digital audio cable (orange) in order to connect two A/V sources.
The following link will provide you with further details:
Hope this helps!