The letter "形" means the shape of a concentric sphere, "理" means radial lines extending from the center of the earth to the celestial spheres.
BAIEN compared the concentric sphere to a ball and wrote the celestial sphere was the biggest. He assigned the character "形" meaning "Shape" from limited Chinese characters resource to sphere. He compared the radial line to a chestnut-burr, and named "理". The character has several meanings. One of them is a sharp line such as a crease or a cut or a notch. It also means a system, discipline, and order.
Although trajectories and shapes of fireworks emitted from the center after an explosion may be a better example for both shapes, Baien chose the static model because the two forms were static.
The top letter "外" which is outer the figure means out space of the celestial sphere. The center letter "中" means the center, "内" means the inner, "外" means the outer space in the sphere. "上" and "下" means upper and lower.
BAIEN knew the existence of gravity in the second half of the middle Edo period. If we think that the center of left figure is of the earth's, we are seeing the celestial sphere from the Heavenly Arctic.
In that case, the center gray aria would be the earth sphere and the atmosphere. And the outer thick black circle would be the orbit of the sun as seen from the earth, and the outermost circle is the celestial equator. If we think the center is the Sun's, the thick ring may be the orbit of the earth. We can consider both possibilities, but BAIEN did not write, which it was. He showed the structure of the space itself.
The figure below is useful for discussing the figure above.
Baien might have considered the figure below, but that is my overthinking.
Because he could use only paper and old Japanese traditional compasses, he could only draw that as a top viewing like below.
Though the upper right figure drew without any lines, it has the essential meaning of our universe. Because the center point means an infinitely small point, and the circle is infinite space.
More importantly, BAIEN thought that infinite space was filled with infinitely small points and that any space became unlimited from the view of a tiny point. Each of our Earth and Sun happened to get them.
BAIEN wrote the infinitely small point is never crushed by any heavyweight. BAIEN named the infinitely small point "無内の中", which means "a point without internal".
If Baien had known the following web site, he must have been very surprised.
Because that was the knowledge he wanted to know most about the part of the heavenly body system which belongs to the visible field of substance of GENGO Theory.