Inspired by a recent threat that I can’t find right now. Specifically about Red Kryptonite. Basically the way it works is unpredictable effects. Turns Supes into a baby, a fat guy, strips him of his powers, etc. But here is the wrinkle. each piece can affect him only once (generally speaking). Say I take a piece of the red stuff and break it into two pieces. Would each of the pieces be a new piece, with its own unique effect? If exposed to one, would he then be immune to the other? If exposed to the “parent” piece, would he then be immune to the “offspring” pieces? You get the idea.
According to Silver Age lore: no. Red kryptonite got its powers when a swarm of fragments from Krypton passed through a radioactive space cloud. Each fragment picked up a differing amount and kind of radiation, which accounts for the differing effects. So just breaking a piece into smaller pieces wouldn’t change the fundamental effects of the kryptonite.
So, in effect, there are actually a bunch of different kinds of kryptonite, all of which happen to have the same color and which are therefore difficult to distinguish, but each kind has its own effect.
Does kryptonite have integer or fractional isospin numbers?
The very nature of red kryptonite suggests that the answer to the OP’s question will vary unpredictably.
It will work in whatever way is convenient for the plot.
Look, red kryptonite was a plot device, pure and simple. It allowed the writers to come up with “what if” scenarios and then play with them. One important factor in them, though – and something missing from superhero films altogether these days – is that Superman has to use his intelligence to solve the problem.
Supe would be immune to the other fragments. The piece that caused him to shrink, turn rainbow colors, be invisible, etc had a specific action on his body due to the particular radiation it had absorbed. When THAT radiation caused THAT effect, it changed Superman’s body to GET that effect. Being exposed to THAT same radiation again, even from a larger or smaller piece, would have no further effect. One bite at the Kryptonian apple, so to speak.