Impedance frequency curves for ferrite beads

I was going through the application note AN-1368 regarding Ferrite bead selection and design. 

I understand the inductive region lies on the left side of the X=R point in the Impedance vs frequency graph. 

But how is the capacitive region determined?

The above shown picture is taken from the application note. Clearly inductive region is left side of the Z=X point. 

How is the capacitive region determined. 

Thanks in advance