It's like measuring the length of a beach, if you measure around every grain of sand, a beach can be infinitely long, I'm not 100% sold on the idea that inanimate object can have a soul, because I'm not entirely sure they have 'experiences' as such, but if you take a grain of sand away from a beach, is it still part of the beach despite being removed from it?
Maybe a grain of sand, like a rock, might have a soul, but then so does a mountain, so does a beach, people have individual souls, but then humanity might have a communal soul as well.
A grain of sand is, after all, simply a rock broken up into tiny pieces, maybe souls get less 'influential' depending on the sentience of the holder.
If you've ever read 'Foundation's Edge' and Asimov's explanation of 'Gaia', I might be able to explain it a little more clearly.