@Damajanti
Hey,
I would interpret that the Control Fix Designator is a Fix (Intersection,Point) in the coordinate system test.
For example Aircraft 68 has to fly to B4 via the Point Zulu. The Point Zulu would then be the Control Fix and the Name Zulu is the designator.
But you do not need to know 100 percent what this stands for, I passed Phase 1 a few weeks ago and even if I didn't know this, I wouldn't had problems solving the task. So it's nothing you have to know detailed.
Regards, Stefan