Lathe axis "positions" - warning stupid beginner ?

Yes, exactly. That number tell EMC2 how many step pulses it needs to make to move the axis one unit (either 1" or 1mm). If you put a minus sign in front of the number it will make pulses in the opposite direction.

www.linuxcnc.org/docview/html//config_ini_config.html#sub:[AXIS]-section

John