Good morning! The first screening is done. Ultrasound shows everything...

Good morning! The first screening is done. Ultrasound shows everything is good, but blood test shows slightly below normal by 5 units (sent for further testing at NIPT). I am 40 years old, have had 3 pregnancies, all my children are healthy, genetically from both sides and from my husband's side as well. Question: Should I worry too much? I understand there are risks with age... Can I do an OMS test? Could there be an error in calculation? Do medications affect the RARR-A test? As far as I understand, these values are calculated by a machine. Thank you for your answer.