40W laser Cross Hair

Hi, i have updated Luban to 1.15 and the controller to 1.20.
When i set the cross hairs to the centre of the plate and placed my object there, i set work origin, run boundary and then i start the laser engraving and the picture is not aligned to the centre.

I read up on the net that the offset of the laser to the cross hairs is Y-21. Not sure this is right as the laser is inline with the cross hairs on the x axis. I offset the x axis by -21 and now it engraves to the centre as required.

Why doesnt the luban software already allow for this?