Just an interested observer (please be gentle). If figures mentioned before in this post are correct, the typical take off weight is around 360 tonnes and the weight entered into the aircraft systems was 100 tonnes less - around 30%.
I assume that, as the take-off was not a '100%' power (please insert correct terminology), the computer systems calculate the amount of thrust required for safe take-off based on, amongst other factors, the entered aircraft weight? Would not such a large discrepancy - 30% - be noticeable, in terms of aircraft performance, early into the the take-off? Putting it simply, if my car tried pulling away from traffic lights using 30% less power, it would be noticed immediately.