Balance adapter 3x 2s - 6s?

[lincpimp]

Yeah, I need to do a drawing, not that I would post it as most peoples kids would do better than I!lol!

I am still not sure how the balancer reads the individual cells voltage in order to match them. I am sure that is is a simple circuit, but having trouble visualizing it.

Not sure how to explain this but how does the balancer know the voltage of the 3rd cell(1st one in the 2nd pack) as it appears that not using the red wire on the 2nd pack would eliminate the ability to measure across the pos and neg of that cell, the purple circle in the attached pic.