multi pin port potential excitation for offset coupler

Hello ,i I have built a layout of a multisection offset coupler, but in order to run we have to define the port , which is a multipin port type, where we have to define the potential in every pin, like shown in the examples bellow.

how do we define the multi pin port in offsett coupler, and what is the intuition behind defining the potentials , so i will understand the logic?

Thanks