You're off considerably. The world population is only 7.6 billion, if every single person on the planet used the internet and 3% were using Linux to do so it would barely multiple hundreds of millions (228 million).
The actual number of users is closer to 3 billion, so even if your 3% is correct (it isn't) that's not even 100 million.
That's also assuming that every user of the internet is a laptop or desktop to access the internet, but that isn't case. More and more people are only using a smartphone or tablet, especially in emerging markets.
The netmarketshare stats have been hovering around this for a few months, and all the "global internet usage" stats that I could find were closer to 3.75 billions.
Even then, assuming 3 billion, it's still 90 million users... that's most than the inhabitants of any country in the european union
The actual number of users is closer to 3 billion, so even if your 3% is correct (it isn't) that's not even 100 million.
That's also assuming that every user of the internet is a laptop or desktop to access the internet, but that isn't case. More and more people are only using a smartphone or tablet, especially in emerging markets.