US measurements?

Ladies!

When the tech measures the baby and it says "6w5d+/-6d" on the screen, does it mean I’m measuring between 6w5d and 6w6d? Or does it mean I’m measuring 6w5d with a 6 days margin of error?? She explained nothing to me and I thought baby was measuring a week behind because she said I was "a little over 6 weeks" but now I’m not so sure because I read the +/- part is actually the margin of error.. Also I know for a fact I ovulated on March 1st (opk + bbt confirmed) which makes it impossible for me to be 6w5d because I did not have sex after ovulation until I missed my period lmao.

TIA!