The 4in1 ESC is just 4 ESCs in one package with power distribution built-in.
The four grey wires S1-S4 are the signal wires for each ESC corresponding to the ESC motor connections M1-M4. The red wire is 5V power supply from the UBEC and the black wire is ground.
The signal wires connect to Navios Servo/Motor PWM outputs as shown in the picture you posted.
You will have 3 servo connectors with just the signal wire and one fully populated with signal, power and ground.