If you were like me and wondered why they had to go back six after going forward five, it's because they counted wrong.
They go forward six and a half turns, and go back six and three quarters.
They go forward six and a half turns, and go back six and three quarters.
The professor talked through a revolution, and then resumed counting from his previous number. The student who was counting in the background just sort of reset to the professor's count instead of correcting him, and it seemed entirely subconscious.
Not mindblowing, but I found that little moment more intriguing than the laminar flow.