There are 4 ports. So you can connect 4 Shifty or 4 BIT to the hub.
Once the Blak Bullet is connected to the system, you will see a popup message for each button that is pressed. It tells you which port number it is.
If you want to attach multiple buttons to same port, that will take a little DIY. In the future we will have a ready made solution for this.
The system works based on voltage level. So you need to connect the wires together (preferably soldered).
Put a resistor in series with the buttons to identify the port:
A - no resistor
Same for B, C, D ports
You can adjust the level with the Button Tuning screen if its not quite correct.