User blog comment:Upquark11111/An Explanation of Loader's Number/@comment-11227630-20171209072636/@comment-26454151-20171209082537

The weakening rule actually is present in Loader's program, just not in my explanation for some reason. I will fix that. The conversion rule is also implied by the fact that all terms are automatically normalized in the way Loader implements it. Also, if you look at the rule for judging the type of Pi-types, you'll notice that the only difference is that in the text you give, the rule requires $$\Gamma \vdash A : K'$$. However, this is kind of implied in Loader's rules as the only way that such a type could even enter the context is if $$\Gamma \vdash A : K'$$ had already been proven. Loader probably figured that it was redundant and not necessary to include it to cut down on characters.