13 and a half safety features.

Chatting to a friend of mine today at lunch I remembered something that confused me mightily at the time. In the new style black cabs in London they sometimes have ads on the bottom of the fold down seats behind the driver. The one that baffled me was an ad for the company that makes the cabs themselves, StageCoach I think it's called, and it proclaimed, in large friendly type, that the cab had 'Over 13 safety features'.
Surely that's 14 isn't it? If it is 14 or more whay not say 'With 17 safety features', what's the point of 'over 13'? it implies that there is in fact more than 13 and less than 14. 13 and a half say. What the hell is half a safety feature? Do you want to ride in a vehicle that has half a safety feature.