Question About Contours (Sketching with planes)

Hey,

So I completed the Soldiworks tutorial "3D Sketching with Planes." I understand the how to complete the tutorial, but I have a question regarding contours within the program itself.

The attachment 3d_Loft_Pic is a picture showing the completed model while displaying the contours. The second attachment is just a sketch I did using a slightly different contour setup. The difference is that instead or arcs leading off from the main circle, I have a straight line, followed by an arc. I just don't understand how the program knows how to apply curvature instead of a straight line for the contours.

I'd like to understand how it works for designing future parts. Any help is appreciated, thanks.

SolidworksSketching