How Myerson expects to hit that number -- also, maths, grammar, logic, etc.
"people buying 2-in-1s – laptops that double as tablets."
That's two devices in one -- take Gartner's 422,726,000, multiply it by 2 (they're 2 in one!!!) and you're at 845,452,000 -- 84% there in one year alone!
"By Gartner’s numbers, Microsoft must double the 2015 number in 2016 and add it again to break the one-billion threshold within three years – 2017."
It appears that the writer here has confused number shipped (Gartner's numbers) with number installed (what must increase by almost the initial amount year-on-year to break the 1 billion mark.)
Even so, that estimation shows a considerable amount of rounding. In actuality, 422,726,000 units installed in year 1 would mean only 288,637,000 new units needed in each of years 2 and 3 -- significantly less than doubling and adding again. Put another way, if the number doubled in year 2, that would be 845,452,000 units, needing only 154,548,000 in year 3 -- just over 1/3 of what the writer claimed would be necessary.
Number shipped would only need to remain constant year-on-year with up to 31% of it in years 2 and 3 being replacements of existing windows 10 units or offset by devices disposed of to reach one billion units installed*. Or if you prefer to think of it this way, starting at 422,726,000 new units shipped in year 1, net new units installed can decline by 22% year-on-year and Microsoft will still have 1 billion Windows 10 devices out there in three years.
Not saying it's going to happen, but it's not quite as absurd as presented.