what does RS mean?

[C-Symh]

Dear author~
Hello！
I have read your paper, but I was confused by a detail:
In Section 3.1, you described the state var as follows: part of the environment o observed by the agent, and then mentioned RS twice, but there is no explanation of RS in the previous or later text. So, what is RS's real meaning?
If you could reply, I will be very grateful!
Wish you a happy life~~~