This is Longomontanus’ diagram concerning eccentricity. The circle is the Sun’s orbital path around Earth. However, Earth is not in the center (M) it is offset to point N. So the path of the Sun while being perfectly circular the days between the equinoxes are not equal.
If Earth was at M then the circle would be perfectly bisected and there would be the same number of days in both halves. Since Earth sits lower down in the Sun’s orbit, the two equinoctial points, are skewed. This creates an asymmetry, an inequality between the two halves from our POV.
You should be able to clearly tell that arc AG is larger than arc GA. It gives an appearance that the Sun is slowing down and speeding up depending on where it is from our POV. There’s always about a week’s difference between the two halves. Of course all astronomers knew it was only an apparent change of speed, not an actual one.
I demonstrated the principle in this video: