Each baby's development speed is different in the early stages, so try not to get too hung up on what the development stage is. I tend to take the week I'm on as a guideline. I'm currently 11+1, so what my ticker says is a general guide of what's going on
I had an early scan at 7 weeks due to a bleed, and the embryo was measuring 6+4, so I assumed that meant it was still in the week 6 development and not 7. So I've taken to looking at the previous week and current week to get an overall idea of what's going on.