Hi Yannis – I'm maybe a little confused myself. I set up an H8000, so that the main outputs feed the ADAT, and the inputs come from the ADAT, which I can monitor on the front panel meters. I then drive the outputs in parallel from Oscillator 440 at 96K.
If I adjust OUT1 Level, the meters show that this affects Inputs 1 and 5. Similarly, OUT2 Level affects 2 and 6. Etcetera. OUT5-8 Levels have no effect.
This suggests to me that ADAT sends 1 to 4 are active, and that Inputs 5-8 are aliases (copies) of inputs 1-4.
I still believe that the actual ADAT channels used are those mentioned in my previous post, but this at least tells you how to set up the H8000 routing (use 1-4 for your 4 channels).