Typically a joystick will send values of a minimum of 0 and a max of 65535. These are the limits that EQASCOM always used to apply internally. If Joysticks are auto calibrating or can be calibrated from their driver then these are the typical values.
Some game pads however don't quite seem to make it to the absolute min and max values (perhaps their centre position isn't set exactly at 32767 or perhaps their hardware doesn't have full 16 bit resolution, hence the calibration screen where the actual range can be determined. The data is stored in the joystick .ini file so the values could be edited manually (perhaps to make the trigger points well within the current limits).
The calibration routine also lets you calibrate the right hand joystick (if you have one) i.e. Z and R (Rudder) axis. In future it's likely that other features such as LX200 focuser options will be available on the game pad using the right hand joystick.