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In the Tattvarthasutra, there is no difference in terms of dimensions. The area in which an atom can exist is called a 'region.' Since the atom is an indivisible part, the field that accommodates it must also be indivisible; thus, both the atom and the region are the same in terms of dimensions. However, there is a difference between them in that the atom can separate from the assembled aggregation of its components; however, the regions of substances like dharma cannot separate from the aggregation of their components.
The ninth sutra contains the term “infinite.” From this, one can infer various infinite regions of pudgala (matter); however, which term signifies the meaning of infinite infinite regions? The term "infinite" is general and can encompass all kinds of infinite numbers. Therefore, the term itself can also signify the meaning of infinite infinite.
Now it reflects on the positional aspect of substances: the position of the substance which is an adjunct to permanence is indeed within the boundary.