The written instructions tell you to install them in one order but the diagram under Verify Your Memory, https://support.apple.com/en-us/HT210103#verify shows the reverse order. Apple today confirmed that instructions are indeed backwards and they will be updated. They may be updated by the time you read this but if the diagram differs from the written instructions, follow the diagram.
Been doing this since cameras went clickety, clickety, clickety, clickety . . .