CRL dating

Most things I read say date by CRL, 6 weeks + CRL = GA

If that is true I would be about 6 weeks 6 days, however my OB is dating me at 6.3. I know it isn’t much different, but does anyone have experience with this question?

I am questioning my LMP like crazy bc of course the one time I think I guessed and entered was November ugh 😑 so I am already looking at least a week behind. Sac and fetal pole both measuring equal to about 6 weeks.

I am driving myself nuts 🥜