Specifying model terms in Fourier fit for curve fitting

I am planning to use the curve fitting toolbox of Matlab using fourier series model (https://ch.mathworks.com/help/curvefit/list-of-library-models-for-curve-and-surface-fitting.html? s_tid = srchtitle).

Is there a reason why we can choose only up to 8 terms (harmonics) in the model?

Why there is no option of choosing more than 8 terms?

Thanks for the clarification