Looked again.maybe this makes more sense
The SENSOR on the engine has a female socket

one wire from the ignition box has a male plug
The tach lead from the box is female
The pug in tach has a male plug on the end
This either plugs into a separate lead from the box with a female socket on it, or a Y connector. the male plug on the Y goes into the sensor female, the tach plugs into the female socket on the Y connector...The box male plug goes into the other female on the Y connector...