Possible to adjust the distance of one of the lead screws?

I just assembled my first CNC, and Stepcraft M1000.

The M1000 has two motors / Igus lead screws for Y-axis. After the assembly I noticed that the distance from the edge differs 4mm between the two sides of the Y-axis. Is it possible to run the motor on one side to adjust it or do I need to pick it apart?

Thanks
Erik