Anyone know about umbilical doppler values?

Dana
My sono tech said to the nurse that I went from 3.8 to 3.1 {doppler} ..I asked if something was wrong and she said no and just told me to come back in 1 week as I'm 34 wks and now should start going weekly. Baby is appx 4 lbs 10 oz so thats good. What She said is driving me nuts im nervous 😒