I agree with you that Dr. Meyer's statement there is very confusing. We know the knot is posterior, and his cut is on the right, as shown. But his description of his black marks seems backwards - but I read it as "single black ink mark" to leftside tail or victim's left, and "double black ink mark" going to rightside tail or victim's right - because that is the only way "cut on the right side of the neck" and "posterior knot is left intact" can work as shown in photo. IMO then the blood spot is on the left tail, but it seems too far toward the posterior knot to be from the triangular abrasion, and may be from some abrasion or ear/mouth discharge that was redacted from the AR. I have not seen photos released of the left side of her face and head where there may be something only the killer would know.