Scaling THCAD-10 input

I want to use the THCAD-10 with a 20 volt input range.

PCW has already told me my maths sucked and I need to use 100k resistors.

What is not clear is if resistors are required on both the Analog In + and Analog In -

The manual says resistors in one place and resistor in another. Can somebody please clarify this please?

In your case its not too important where the resistor(s) go.
As long as you add a total of 100K series resistance to the inputs
you will have a 20V full scale range.