Lemur XY control Zebra AU

I'd like to set up 4 multiball instances in lemur for iPad and map those to the 4 XY controllers in Zebra.

I've set them all up so each x and y has its own unused cc value but when I map then: x to cc 100 and y to 101, for example, they link to zebra's XY controller ok but I'm only able to move the controller diagonally, at this angle: /

Pretty sure I've missed something simple. Any ideas?

Thanks