Let me explain this further. In some Wholes, like the Slime Mold (See HERE in the Essay What is an Individuum, Part 3), being-a-unity is already varying. But most conspicuous is the variation among the different Wholes (i.e. as compared with each other). The different beings occupy different positions on the scale
Thus it is proper for Substance (not necessarily a certain substance pointed to) to manifest itself in different degrees of being-a-unity. The unity of Substance is always : a unity in a certain degree (not excluding a possible 100% degree in some cases).