PWM Controller for known f(t)
The maximum value minus the minimum value of the repeated sequence signal block should be equal to the maximum value minus the minimum value of the input signal.

Your input signal ranges from 0 to about -0.13.
In your diagram, the repeated sequence signal block is a triangular waveform.
So, the amplitude of the triangular waveform should be about 0.13 / 2 = 0.065.

If you set the amplitude lower than 0.065, the PWM signal will 'clip' and you will lose information.
If you set the amplitude higher, you lose accuracy, because you use less than the maximum 100% PWM to represent the input signal.

Still, setting it to 0.064 would yield results that look quite similar to the PWM signal with the triangular amplitude of 0.065 and it shouldn't be mostly ON. Same for setting it to 0.066, it shouldn't be not mostly OFF.