Print a cross-hair with crop marks and then print and cut it. Now go into the menu and find Mark Detect. Enter into that menu and then hit enter a few times until you see X Offset and Y Offset. You can adjust those settings to make the cut more accurate. Just remember that Mimaki does things backwards. So the X is actually up and down and Y is left and right. Also, left is positive and right is negative.
So if you print and cut the cross-hair and the cut is up and to the left of where it should be, you would adjust the X offset and Y offset negatively to move it down and to the right. Rinse and repeat until it's spot on.