They go from your last period so it means you conceived approx 22w5d ago, about 2 weeks after your period started
Well when we did that i was due on 22nd july but when i had my scan the put me back 2 weeks which is why i'm now due on 2nd August.
I still think its about 22w 5d since you conceived. You must have ovulated late after your period. Even if people have ivf and they know the exact date of conception they add on 2 weeks before it as the start of the pregnancy.
