I'll start with some critique on the experiment:
first the measuring system used: yolol ticks are not a clock.
Even just looking at the timings of one 4, 3, 2, 1, 0 run with the U-tool shows that:
7.37 7.57 7.81 8.01 8.24
Which means that your J++ will be smaller than it should, because yolol...