Yeah, I may have sacrificed clarity for concision in this case.

To answer by way of example, if you are given "add R1, R2, R3" rotating to the right will result in "add R2, R3, R4". As another example, rotating "mov LR, R0" to the left will give "mov R12, SP".

In other words, rotating right changes every register RN in the instruction to be the register R(N + 1). Left changes RN to R(N - 1).

My hope was that if it was not clear from reading, it would be after testing things out. But hearing that this may not be the case is helpful feedback!