Am I an anomaly?

My blood pressure is 123/47...pulse 79. The systolic # (123) is normal and yet the diastolic number is really low (47). I understand that normal diastolic numbers are usually between 60 and 80.
I have been on a glandular adrenal supplement for 2 years which has basically had no effect at all on my blood pressure. At the time I started the supplement it was about 115/50.
Any suggestions why this would be and should I be concerned?
Thanks much.