I don't know anything about Gurtner carbs, but from what it looks like to me-
All the cables on my moped has 1 ball end, 1 open end.
So, I am figuring, that you're supposed to put the end of the cable without the ball through the bottom part of the choke hole, going upwards then the choke slide goes on top of that, with the pitted end down, so that the ball holds on to it- and then the spring follows and the top goes on top of it.
Attached is a pic to show you what I mean. Please note that the "hole" as I labelled is actually on the other side and is the choke hole itself.
Of course, it's just an educated guess. Hope I'm right about this. Dan Adams would be able to verify.