a bit help on sound connections

just bought:
http://www.newegg.com/app/viewproduct.asp?DEPA=&submit=Go&description=AV49N

for my friends computer. he has 5.1 speakers. 3 connections needed to be connected to the computer. front, rear, and center/sub

now according to the shuttle board it has 6 channel. i know it doesnt say 5.1 but it looks like for the connections it only has front, rear, and mic.

im kinda confused how to connect them.

I think it's talking about the 6 channel processing capability, not outputs. It means it can handle 6 independant channels at once.