The only manual I have is one of the photos (attached) and in the eBay listing description;
1, fully support of MACH3 and other computer software support for parallel port control.
2, USB power supply and peripherals powered phase separation to protect computer security.
3, peripheral wide voltage input,12-24V, and anti-reverse function.
4, all of the input signal, all the light lotus isolated, which can be accessed emergency stop on the knife, the limit to protect computer security.
5, all the way to the relay output port, control spindle switch. Output port P17 mouth.
6, all the way through the optocoupler isolated 0-10V analog voltage output can be controlled with the corresponding analog interface converter to control the spindle speed. Output port P1 port.
7, open all 17 ports, which can be accessed with the optocoupler drive, 5-axis stepper motor can be controlled.
8, P1 as PWM outputs can be controlled with optocoupler input spindle governor.
9, can be accessed by a common cathode or common anode input level to 5V drive.
Having read it I now know that P1 is the output that will make 0-10V work.
I followed the link you shared and found that I think I needed to invert my pin. Once I did that I noticed that when the spindle is set to 1.0 speed it has 0V and then anything from 101.0 to 3000.0 has 1.4V. I’m not sure if I need to edit a range or something in order to achieve a higher voltage?