on the red line?
~1/2 of them are directly on the line, a the other 1/2 are more or less equi-distant on either side of those. This is caused by the rounding seen in-game. the lesser values are 0(I am confident there is still some small % increase in effect), and the greater values are where the rounding causes the opposite.
A similar effect, combined with some missing data in that range creates the strange blob underneath the green curve.
I should also note that the trend line on that graph are extended beyond the data they represent, so as to visualize where they meet.