it is much easier - any digital device (powerbar or dosing unit) can be addressed

that means: assign numbers 1-4 to the pumps of the dosing unit (this is default) and addresses 5-10 to sockets of the powerbar, then daisy-chain the control lines and connect them to S1-4

more about the addressing can be found in section "extras->digital-powerbar->numbering" of the manual