Thanks for the response, and I apologize that I didn't have the direct quote from William's.
Williams Textbook of Endocrinology, page 703 says, "In the circulation, total testosterone is composed of 0.5% to 3.0% free testosterone unbound to plasma proteins, 30% to 44% SHBG-bound testosterone, and 54% to 68% albumin-bound testosterone". I read that as William's saying that SHBG is 30-44% of TT, not bound-T. It still seems to contradict Labcorp's "the majority (approximately 60% to 90%) of serum total testosterone is associated with sex hormone binding globin (SHBG)".
There is a newer addition of Williams Textbook of Edocrinology, which might have different numbers. If so, I apologize. It may be possible that the accepted values have changed in the last four years. Does anyone have another source that states the amount of SHBG-bound T?