The first bits code for the channel the data is coming from.

@gizmo: I noticed that behavior too. The offset is shifting the average voltage for the cosine. It is helpful when using attenuation to produce 1/2, 1/4, or 1/8 VDD amplitudes and you want to shift that smaller cosine's average voltage up or down. So, the offset can be negative as well. I am not hap...