Just to make things clearer I’ll explain the cardinals.

All Circles and Arcs have Cardinal points which are a special vertex that will scale the circle or arc. They are called Cardinals because they are normally found at North, South, East and West, the cardinal points of the compass.

To find them use the move tool with Nothing selected, when you move over an edge the move tool will auto select, the circle/arc will turn blue, but as you come to the Cardinal the blue selection will disappear (meaning it has selected the vertex that is the cardinal) click and move and it will scale.

A circle has 4 Cardinals, which is why we recommend always using a segment count divisible by at least 4. 12 is better but not essential.

This mean the cardinals are easily found on axis, four to a circle and midpoint on an arc.

So having typed all that, try this exercise.

Draw a circle on axis (meaning pulled out on red, green or blue direction), find the cardinals and resize a few times.

Now draw a square that hits the four vertices on the circle, not just a random square shape, this will split the circle into 4 arcs with cardinals at their mid points. Find them and move them in to the edge.

If you get that right then just extrude the circle before drawing the square and do the same.

Here’s a demo of what I describe.