Suppose that we wanted to maintain that there are Chronons (an A-theorist might want to maintain as much). Now, suppose that we adopt a view according to which Chronons are all differently sized in just the same way that ancient Atomism, and perhaps early modern Corpuscularianism, suggested that atoms of matter came in varying sizes and shapes.
Could this be affirmed? No, because, it seems, each Chronon would be incommensurable with any other Chronon (and this follows, it seems, from the fact that each Chronon would represent or be co-extensive with, on A-theory, a discrete logically possible world). However, it also could not be affirmed that each Chronon is the same size as any other (which follows from incommensurability). It could only be said that Chronons are each indivisible units of time.