OK, as one of the children with a phone, am I hearing here that takeoff configuration is commonly setup to use every inch of available runway ? That takeoff looks like it allowed for less than 1% margin. I confess that I find that surprising. Wouldn't a soft tyre, an ingested sparrow or even an unexpected squall of wind up the chuff have a bigger effect on take-off distance than that? Or is there time and information to allow you to detect that you are not precisely on the expected speed-distance trajectory and give it a bit more wellie ?