Here are the calibration instructions from per 7 of
this document.
6) Calibration
The calibration procedure takes the minimum, maximum and center
values of the PWM input signal and scales the output based on these
values. Calibrating the Talon will allow full range of control with PWM
signals that are not within the default range. Calibrating will also
correct any non-center issues with input devices such as gamepads
or joysticks.
To calibrate the Talon:
1. Press and hold the button labeled “CAL” with a paper clip. The
LED should begin to blink red/green.
2. Continue to keep the button pressed while moving the joystick
full forward and full reverse. You may do this as many times as
you like.
3. Center the joystick and then release the CAL button.
4. If calibration was successful, the LED will blink green several
times. If the LED blinks red several times, the calibration was
not valid. If this happens, the Talon will use the last valid
calibration values.
All calibration values are retained after power cycle or reset.