Column in matrix visual

[mfeingold]

I have a matrix visual that shows aged debt, like this: 

Client name	0-30	31-60	61-90
ABC Ltd	£100	£0	£200
DEF Inc	£0	£10	£20

I'd like to include another column (ClientCode) which is an attribute of the Client record. So it would look like this:

Client name	Client code	0-30	31-60	61-90
ABC Ltd	0001	£100	£0	£200
DEF Inc	0002	£0	£10	£20

I've tried adding the ClientCode field in various places within the Fields section of the visualization but I can't seem to make it appear as I want. The rest of the matrix, including the totalling of the fields works fine.

This sounds simple. What am I missing?