Altitude/Airspeed of AI pilot not doing anything

I have the “Delegate control to AI pilot” key set and I use it frequently. However, there are two sets of hotkeys that I’d like to be able to use: the one that lets you adjust the preferred altitude, and the preferred airspeed.

I’ve got both of those set but when I press them while the AI pilot is in control, absolutely nothing happens. Is there some trick to it?