The idea is simple. Imagine an apple in your mind. Now, compare it to the chart.
Did you...
See nothing? (5)
See a rough outline of an apple? (4)
See a rough 2D shape of an apple, with no colour? (3)
See a coloured 2D shape of an apple? (2)
See a fuly fledged, 3D shape, texture, the full shebang? (1)
Now, my problem already is that I don't fit into these boxes. If I imagine an apple, i can feel its coarse texture; smell the sharp tang of it; see, in quite good detail, an impression of an apple. But only in minute detail for one small area of it.
As soon as I try to move the image in my mind (say, to look at the bottom of it) I can't. Or, if I can, I completely lose the first image.
I'm even worse with faces. Ask me to visualise someone, even my wife or kids, and I'll be able to imagine their hair, but not their face; their eyes, or their nose, but not their hair. I feel like my mind turns images into a picasso painting.