Man, at the end of the day its all hormone driven, and plants vary.
Using the math can help increase the chances that the auxin will turn your cut job into multiple tops, but there's no guarantee. I'd try and use the FIM technique as well as count the nodes.
Fwiw, I topped a plant (before I saw that guide) and did it at the spot he was talking about (I just counted up from the first leaves (not the round cotyledons, the other ones with just 1 tip) and let it grow to where the sixth node was just barely starting to grow, then cut it (so the cut was between the 5th and 6th from the bottom). I wound up getting 6 tops, but one of them was really weak and broke off, and one is small and growing slower than the rest, but its worked out really well. I have one more round of topping to do and she'll have 28 true tops. She has 14 now and she's only about 5 inches tall.
Edit: here's a pic of it
View attachment 2779330
Something that I think helped the fim, when I cut the tip top off, the side branches (that BC the tops) were reallllly small. Usually when you top, the part that is cut stops growing bit I cut mine really low, to where you couldn't really see what was goinng to grow. The two branches grew as tops, plus 4 grew out of the middle (the part that was actually cut)