the reason for it is that the incoming audio thats being recorded to the track, will only show on that track meter, not the bus or master, once the files are recorded in sonar, and you play back, the signal will then be sent from the tracks to the sub bus and master, not while recording tho , while recording its being written to disk, so there will be no out put from that channel till playback, i wouldnt be concerned about sub busses or master bus till mixing