You're right that that's a very tricky conditional claim, lsat_novice, because the language does seem to suggest that if either K or R is included then both must be. But that's not really what it means. Rather, there is an implied "or" in the sequencing portion of that diagram, as fleshed out in the explanation that follows on those pages. What this rule is really saying is that if K is included, Q is before K, and if R is included, Q is before R, and if both K and R are included, Q must be before both of them. Treat that rule as splitting into those two rules about the Q-K and Q-R orders, and it should make more sense. Also, the contrapositive will become much easier to diagram and to understand:
(
Q 
K)
K (if Q is not before K, then K is not included)
(
Q R)
R (if Q is not before R, then R is not included)
Thus, one hypothetical you might play with here is "what if Q is last?" That would mean that neither K nor R would be after Q, and they would both have to be out. Since only two variables will be out in any given solution, all the other variables (D, G, I, M, and Q) would be the group, with the order of DGI and M being completely undetermined.
You might ask how you are to know that the "or" is implied, and that's a fair question. The answer is just as you put it - that without it, the rule doesn't make much sense! This is supported by the portion of the rule that says "if either are interviewed", suggesting that they don't both have to be.
Good eye and good question! I hope this helps clarify it for you.
Adam M. Tyson
PowerScore LSAT, GRE, ACT and SAT Instructor
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