Aha. I see how it can be confusing. 
The "red wire" is meant to be a momentary connection. Each time you make the connection, it generates one +5V trigger pulse.
My observation after looking at the actual board is that you can make this same momentary connection by shorting (using a metal screwdriver tip in the video) two adjacent components. The "orange line" in the schematic shows this momentary connection. Again, each time you make the connection, it generates one +5V trigger pulse. It is just happen-stance (dumb luck?) that the board was configured in this way such that you don't need to add a temporary wire for calibration.
Not sure if I'm being clear 
