The PC joystick interface used by DOS games provided the following:
- 4 analog axes (joy1 vertical, joy1 horizontal, joy2 vertical, joy2 horizontal)
- 4 on/off fire buttons (intention was for 2 buttons on joy1 and 2 buttons on joy2)
The game is asking you to circulate the stick so that it can determine the voltage limits on the analog axes because each joystick has different limits on its electrical resistance that is used to determine the positions of the analog stick.
I have no idea how the dosbox mapper works though, so I can't address issues with that.