Select the direction you'd like the input to move the mouse. Adjust the movement speed using the slider underneath. If you're mapping an analog input then this is the maximum speed; for a button it's a constant speed.
The speed is independent for each input. You can have faster horizontal movement than vertical movement, or map one set of inputs to a fast speed and another set to a slow speed.
Select the mouse button you'd like the input to simulate.
Simulated scrolling can be smooth like the scrolling gestures on a trackpad, or discrete like a mouse wheel that clicks as you spin it. You can simulate a vertical or horizontal mouse wheel.
To use smooth scrolling check the Smooth button and use the slider underneath the arrows to adjust the scrolling speed. If you're mapping an analog input then this is the maximum speed; for a button it's a constant speed. Scrolling will continue as long as as the input is held down.
To use discrete scrolling leave the button unchecked. The input will trigger scrolling by exactly one line and stop, regardless of how long you hold the button down or how far you move an analog input.
The arrows indicate the direction you would spin a mouse wheel or move your fingers. If you use natural scrolling you may need to choose a down arrow to scroll up and vice versa. You can also change this globally in > System Preferences… > Mouse and > System Preferences… > Trackpad.