Anche a me la logica mi pare più giusto così 
ma il tutoria dice:
The 8-relay board shown here gives you a choice of powering the relay drive circuits from the same supply as Arduino, or isolating Arduino by removing the jumper over at the right. In that case you need to have some separate +5V supply connected to GND and the "JD-VCC" pin (whatever THAT label means...). Here's a closeup look at the pins:
If you isolate Arduino, you need to connect +5V ONLY (NOT GND) from Arduino to the VCC pin. The Arduino output pins go to IN1 through IN8. And again, these pins are Active LOW.
è sbagliato??