curriergroh is correct. The indication of "3/2.1" means that the input signal is three discrete front channels (L/C/R), two discrete surrounds (SR/SL) and an LFE channel, which is the ".1". Add 'em up and you get "5.1".
An additional note, if you're not that familiar with surround. Even though the incoming data stream may have the 5.1 channel configuration, you won't hear something from all channels, all the time. This is normal, as the mixers distribute sound to the channels as the on-screen action dictates.
The best way to make certain that the connections to your speakers are correct is to run the 1070's test tone. To make certain that the decoding is working properly, use a test disc such as Video Essentials or Avia.