There are many interpretations of the three thousand worlds.
In Lu Bei's original plan, a single leaf, a flower, or a blade of grass represented a small world, as did the sun, the moon, and the stars, each conforming to the concept of a small world.
Taking one thousand as a whole number, one thousand small worlds constituted a lesser thousand worlds.
One thousand lesser thousand worlds made up a median thousand worlds, and one thousand median thousand worlds formed a greater thousand worlds. Because of the progression from small to medium to large, they were called the three thousand worlds.
Countless worlds formed a multi-dimensional universe space, centering around the Central Great World and extending outwards, with innumerable dimensional spaces, thus countless three thousand worlds.
Thus, the Great Heavenly Monarch, the Heavenly Emperor, ruled over the myriad heavens!