If you take the exit straight on to 443 and go off at the Ramot exit and go on Route 1, I would imagine it would take about 25 minutes, but you’re right, it’s an exaggeration and does not make for good advertising.
Just as an aside, I looked at the ad one more time and see that it says “10 minutes from the center of Jerusalem” not about the Kotel. Someone else mentioned the Kotel comment as well, so perhaps there was a change in the wording of the article. Anyway, I just want to add that for most of the people who live in this type of neighborhood, “the center of Jerusalem” is more likely the Geulah area or the shopping areas around that, but even so, there are definitely ways to make this trip in 15 minutes as I know someone who gets to Har Nof in the mornings in 20 minutes.