I'd like to know where you got that figure. The statistics used to say that 7% of pack a day smokers got lung cancer. That is 7 out of 100.
“I’d like to know “
Stuck in my head from at least 10 years ago, I can try to look up. Note your stat refers to pack a day. The 1 in 6 refers to all smokers, i.e., including those over a pack a day.
Other number that stuck with me it takes 30 “pack years” (1 pack a day for 30 yrs or 2 for 15, etc.) to present irreversable and noticeable pulmonary reduction in later life compared to non smokers, measured in FEV - forced expiratory volume.
I started to search but the following came up quickly and for a more recent study (2018) with a close approximation to the 1 in 6:
https://www.verywellhealth.com/what-percentage-of-smokers-get-lung-cancer-2248868 There's table that indicates (for male smokers), chance is 14.8%, which is about 1 in 6.75.