If the soul is changeless, then how does it change from its svarupa to a seed form?

From: panca pandava das

Prji in your class you mention that soul has dimension like krishna, radharani has, similarly soul has like certain heights etc. and then you  mention when soul get material body his dimension become seed form so my question in B.G. 2.24 prabhupada translation was soul eternally the same(changeless) then why soul change dimension.