You should not breakdown Marketing Channel by Referring Domain.
Assume if the visitors click on SMS link with Tracking Code starts with 'SMS' and land your website. Since because you have proper Marketing Channel Processing Rule, under Marketing Channel it will go under SMS.
But the referring domain was 'empty' here (Since it is from SMS and no referrer). So if you break the Marketing Channel by Referring Domain, it will be 'Typed/Bookmark'.
So, please use 'Marketing Channel Detail' to correlate.
There were plenty of discussion went on related to this topic and you can search for it inside the Forum. I would try to post a Blog on it.