Which chart is more accurate?

I have been testing earlier than I used to because I’ve been waking up (to pee and just naturally in general) earlier, for the past week or so. However one chart says I’m at 12 DPO and the other says 13, and they also estimate different start dates for my period. Which should I be following? I have been period tracking here for 5 months, this is my first month using fertility friend. But my first full month tracking bbt in either.

Also, how many days before my period would I see a temp drop below the line?