Those are just guesses. And that means 9 weeks of flowering once you flip to 12/12. If it's an auto should be done in 9 weeks but that's all just a guess. Could be more or less they are literally just guessing most of the time.
And depends on when you start counting the flower time. Just bc you flipped the lights 12/12 doesn’t mean you start counting. I always start counting once I see pre flower. Could be 2-3 weeks after the flip more or less.
I always thought it ment from flower but just bc you flip to 12/12 doesn't mean it's flowering that day. I've seen some that say 76-80 day but those that have grown it say "120 days". It's kinda an estimate IMO.