As I said, the screenshot in HOL has a watermark, it has been tampered with.
Whoever saved the PNG did so with a palette that has many more colors than those ACTUALLY USED.
Ian's figures are correct.
Use proper gfx tools for color counting and do not use HOL screenshots as gauge (I used the same screenshot you posted, Galahad, and as I said, i got to the same result, because of what I said, details you are overlooking).
You can get a shitload more colors using copper reloading but not as many as 1082 at the same time on screen. Not even 800.