Pre screening test for Down syndrome


So my doctor called me this afternoon and mentioned that my score or level was at 42 just below the positive mark. I have to have extensive ultrasound with a specialist and have other test done. She said the positive mark is at 50 something... I can’t remember. Does anyone know the count or level? Should I worry since she was to do this because of my age which is 39 and I have had several previous miscarriages?