Gads,
If I recall correctly, you have to enter steps/rotation (motor/driver 200 fullstep, 400 half step, 2000 10microstep, or whatever), gear ratio between motor and screw (direct drive 1:1, or gear ratio) and the turns per inch (tpi) of the screw.
To report an error I would suggest going the the irc chat on linuxcnc.org.
They just released 2.2.3 which includes some fixes to stepconf.
Alan