the amp is internally bridged... there is just 2 positive and negative outputs to make it easier to hook up multiple subs.
i had a directed 1100d and it was like that, dont worry, i was confused at first too
just wire it up like you're wiring a normal mono amp, except now you can put each sub on its own terminal, it makes it alot easier, theres no twisting of wires involved and all that nonsence.
i want it to run at 2 ohm because it isnt .5ohm stable i have 2 dual voice coil 2 ohm subs each sub would be running at 4 ohm then connected together for 2 ohm so basically if i connect 1 sub to 1 channel and the other sub to the next channel it will be at 2 ohm getting full power out of the amp