OK, just went into phone on the car, here is what happens:
press the phone symbol on the steering wheels, a voice comes on and says "would you like phone or navigation" you say phone, then 5 items come up on the screen and the voice says "would you like to Dial a number, vehicle phone book, hanset phone book, call history or international call?"
You say vehicle phone book, it says "vehicle phone book, please say a number from one of the listed numbers" The 5 stored numbers come up. You then just say one, two , three four or five and it dials that number.
If there were more than 5 it would be hard to look at the screen and scroll down so you could call number 25 on the list. With 5 , you just glance for a second as you say "two" or "three" etc.
I went into phone settings and there are only 5 for that screen, when you press "add new" it is a frozen tab since I already have my 5 most called numbers there.