I have memories of opening up all the windows in my apartment, so I know I have one in the bedroom and one in the living room. The memory is more "felt" in the motion of my arms in unlocking and sliding said windows than "seen". If you asked me how many panes of glass it has, I couldn't tell you. At least two, because it opens by sliding sideways, and that doesn't move the whole window. Are there crossbeams subdividing the two portions vertically or horizontally? Maybe a grid? I couldn't tell you. I can't even tell you how many panes of glass my mental image has, it's too indistinct.

Having just now stood up to check - it looks like the answer is 3 planes of glass for the living room window, which I never would've guessed. The two sliding panes, undecorated aside from their frames, and then another fixed pane above - presumably so the movable bits aren't as heavy by reaching all the way to the ceiling - with a wooden lattice/grid subdividing it into a 2x6 grid.

I personally don't quite have aphantasia - I do have the ability to (very weakly) visualize. It's so weak I grew up thinking the "minds eye", "visualizing", "counting sheep", and "memory palaces" were all overly flowery metaphors that meant thinking non-visually about concepts. I didn't get the draw of scenery descriptions, and still can't effectively turn them into worthwhile visualizations. I was never disturbed by the characters described in books looking different than I imagined them when a movie was made, because I'd never imagined them visually.

Say reality has a vividness and observable detail of 10. Dreams also rate a 9 or a 10 when I experience them - subjectively indistinguishable from reality except by realizing that what I'm experiencing might be "impossible" by the rules of the world as I know them, and that the more likely explaination is thus that I'm dreaming. On the other hand, visualizing those same dreams from memory - or visualizing any other memory - might only rate a 1, if that. Trying to visualize a non-memory - e.g. trying to visualize "a beach" if I don't take the specific effort of thinking of a specific beach I've been to before and trying to remember that beach specifically - I get the outline of a circle, and two straight linear lines - without color or texture or anything, representing the sun, the horizon, and the interface between sand and sea.

I'm semi-convinced this is partially down to habit. My default pattern as I go about my day is, when seeing things, to reduce them down to their concepts first, and then to remember those concepts, and then to later recall those concepts and reenforce those memories, rather than the weak and forgotten visual memories, which in turn means a very weak mental visual library from which to draw from for synthesizing visualizations, and very little practice remembering or recalling such memories.

As an experiment along those lines - I made a point of observing and remembering the visual representation of various lane-merge road signs during a commute. Turns out there's a bunch of different patterns in various rotations - mostly yellow, but some orange. It's still a memory heavily renforced by concepts - the 3 dashes of one pattern, the S-bend shape divided into approximately thirds. I could draw them pretty accurately. Ask me to draw a speed limit sign and... well, I know the color scheme, and there's a large number, and I could tell you where several are and what the limits are. I think they say "speed limit" on them, but I couldn't tell you if the words go above or bellow the number, or maybe both? Perhaps it varies by sign? Is there a "MPH" too? I have remembered that road signs are ALLCAPS and sans-serif (by straight up realizing those were questions I could ask and answer for myself by observing reality), so despite not knowing where on the signs the words go, I at least know what the shape of the letters should be pretty accurately.