Help please - clear blue week detector

Just wondered from your experiences how accurate the weeks detector is on the clear blue pregnancy tests? Glow estimates me at 5 weeks today - this is from the first day of my last period, but I took a clear blue yesterday which said I was 2-3 weeks (which is likely to be from the exact date we conceived).

This is my second pregnancy but I just can’t remember the maths of it! 🙈 is how many weeks calculated from the day of your missed period or the date you conceived? I’m confused! 😂 I can call it baby brain right?!