Is the Dynamic Time Warping constraint Itakura Parallelogram based on series length?

I'm looking into the Itakura Parallelogram global constraint for Dynamic Time Warping.

I am confused about the maximum width of the parallelogram, is it solely based on the length of the two time series being compared, or can it be varied to achieve a bigger or smaller warping window?

The maximum width (or the length of the smaller diagonal) of the paralelogram is implicitly dependent on the maximum allowed delay (or distance), around the middle of the signal. In this example figure (taken from here), the maximum allowed delay is $dt=4$ and hence the length of the diagonal is $\sqrt{2} dt = 5.66$.