Quick question regarding integration order in Generator 2D model

Hello all,

I have a quick question regarding the integration order of the z component of the electric field in the example model "Generator 2D". In the example model the order of integration, and thus the order of the polynomial used to solve the integral, is listed as 4 for the integration of the Area and the two Voltages of the magnets. Why is the integration order 4? Why not 3? Or 2 since we are dealing with a 2D model? Is it just so that the solution to the integration is more accurate? Would integration 3 or 2 work for this example model?

Basically I am asking, how do you decide what the integration order is?

Thanks so much for any help on this question.
Stephen