In the video, the cross sign on RS box dissapeared at 1:48, but it should NOT have been gone!
Relevant lessons: Introduction to sequencing games
At 10:55, J.Y. says, "you can put the H either here into 1 or you can stack the HS together" But you can't stack the HS together in this case. Q16 says, "the list of the sections located in aisle 2" and the answer choice (E) lists M R S as a full list, so you can't stack the HS together in the case of (E).