Does "one particle per 10 billion" mean "one particle among 10 billion antiparticles"?

To me the way I read--it means if you had 10E9 grains of black and white sand on a beach --I'd have 5E9 grains of white sand and 5E9 plus 1 grains of black sand.

Rap

More confused.Let's see whether someone will come up a clearer answer.

1- The universe is composed of particles and antiparticles.
2- For each 10,000,000,000 of antiparticles there is 10,000,000,001 particles.
3- The exceeding particles form the stars and other astral objects.

Yes, it seems so. Must be an editing failure there.

With respect to the question in the title:

(1)"almost equal amounts of particles of antiparticles" (i.e., almost, but not quite equal)
(2)"except for a tiny asymmetry:"--just repeating what was said in (1) with different wording

So, then, the question is "how close to equal?" and/or "how tiny was the asymmetry?"

Answer: One particle per 10 billion

This is perhaps a little ambiguous, but it's a big-ass number, either way.

Unlike Raprap, I would read it that for every 1o billion anti-particles there were 10 billion + 1 particles.

It certainly does not mean this: "one particle among 10 billion antiparticles," as suggested in your title.

In this context, "per" intends a ratio. You might read it as "for each ____"

Here the blank would be filled in with "10 billion"

Per cent (percent) is an abbreviation for "per 100"

I say that because, to me, the choice of the word "among" suggests that there's only 1 particle for every 10 billion anti-particles.

It could be read differently, I guess.