Yes, I think you're right. In another section of the documentation ("Information Services"), it lists the same service as SVC8, not SVC7:
...the double opt-in tutorial assigns the service, "Book of the Week" to SVC7, and not to the above (SVC8). So if we follow this, then this is the missing SVC8 that the other tutorial was, I guess, referring to. And I should correctly assign the second line of code to SVC7 in the double opt-in tutorial.