steinberg ur44 output 5-6

Hi there,

I'm setting up a home studio with the new Steinberg UR44 using Logic Pro X. When assignig track outputs, I get the option of 1-2 stereo, 3-4, 5-6.

The steinberg UR44 has also 6 outputs: line outputs 1-2, 3-4, and LR main outputs with a level knob.

If I assign the track output to Stereo Out in Logic Pro, the audio plays through the UR 44 Main output (with volume control) as well as through output 1-2 with no volume control.

If I assign the track output to output 3-4 in Logic Pro X, I get a nice line level out of output 3-4 rom the Steinberg UR44 which is sweet for isolating lets say a drummer track.

But what is this output 5-6 in the Logic ProX output options? I tried it and I get a half signal (low and mids only) coming out of all the outputs of my UR44. What's that all about?

I would be happy to have a 5-6 output working but I can't figure it out. Any clue?