And you are supposed to Stop by the end of the Stopway; if you execute the stop no later than V1-ish, give or take the current 1 or 2 seconds. And looking at he photo in post #65 there doesn't appear to a lot of stopway. And given that the braking action of grass is unpredictable, but certainly significantly less than tarmac, how they ever make a sensible calculation that you should stop within the stowaway defeats me. I wonder what coefficient is used for the last bit: it can't be the same as tarmac, unless they factor in the wheels sinking up to the hubs, but that doesn't happen instantaneously. It's not like an F1 gravel trap.
We'd need to know where on the runway V1 was called & Vr and how the rotation was executed to be sure of anything; but I can categorically say that on all the diverse european runways I've operated from, B732/3/4/7/8, I don't remember seeing the end quite so close as that. I suspect the wheels were still down as the crossed the end of the tarmac.
It does concern me that, with i-pad performance, there seems blind faith and little understanding of what is going on when the numbers are entered into the FMC. Pilots do their CPL & Perf A course. They know the rules inside out. Yeah, but what do they really mean and what does it look like 'on the day'? They then assume, correctly, that the i-pad has all the reg's in the program and the numbers in will give the correct legal numbers out. But that has removed all 'feel' for what is going on. It's just another 'magenta line'.
I used to teach the 'gross error check' philosophy, especially with takeoffs & load sheets, TOD's distance to go, etc. Guys asked, "what's the point? We have the FMC" "So you have a feel what what's correct and not, and because some other guy made the load sheet, but I sign for it, and because I don't always trust the FMC. It's tool not my wife who must be obeyed." And now there is the i-pad.
Sure enough we detected a 10ton error in the load sheet. One day someone else didn't and they had a tail strike.
Same with performance. If the calculated N1% seems too low, it probably is. But you'll only know that if you have an idea of what is a correct range; i.e. paid attention on previous trips.