I believe the total deaths in the U.S. in a typical year is around 2.5 million, so that figure is definitely exaggerated, if you're talking about the U.S. alone. On the other hand, if you're referring to world population, I'm inclined to think it's grossly understated.
Smoking is a real bugger when it comes to causing deaths from vascular disease, coronary disease, respiratory disease and various forms of cancer. I can't imagine why anyone would even need to make up numbers to exaggerate its significance in causing crippling illness and death. The numbers are sufficiently high without any embellishment at all.
Since smoking causes these problems, I suppose no non smokers ever contract the diseases and every smoker contracts them. Right?