How we cite our quotes: (Chapter.Paragraph) Note that chapters aren't numbered, so need to be numbered manually, 1 to 14.
Quote #4
I persuaded myself that she had only been play-acting, that she had wanted to frighten me and had taken an overdose by mistake. (5.37)
Kelvin is acknowledging that the Rheya in his head is not the same as the Rheya in reality. There are multiple Rheyas even before there are multiple Rheyas.
Quote #5
"Certain events, which have actually happened, are horrible, but what is more horrible still is what hasn't happened, what has never existed." (6.80)
Snow is saying that the real reality can be bad, but fantasies or versions of reality that never happened can be worse. This seems to suggest that fiction is worse than fact. Which seems hard to credit; horror movies deefinitely aren't worse than the Holocaust. In any case, since Solaris rather scrambles what's real and what isn't, it's not like Snow can tell the difference between what's happened and what hasn't anyway.
Quote #6
"I saw something which looked like a garden. Yes, a garden. Trees, hedges, paths—but it wasn't a real garden; it was all made of the same substance, which had hardened and by now looked like yellow plaster." (6.180)
Berton sees a garden made by the ocean, and it actually looks like a fake garden. It is a real fake version of reality, and a fake real version of reality both at the same time. You half expect the ocean to make a department store with talking dummies next.