Purpose of his article is to clear the illusion from a lot of people's minds that Sachin Tendulkar is the best batsman in the world on the basis that he has got more centuries than anybody else.
Coming straight to the facts,
Sachin has played 177 test matches to date. Generally a batsman gets 2 innings in a test match. Sachin mostly played in upper order so there's a good chance he has played most of the second innings as well. He has played 453 ODIs.
Total innings to date Sachin played are 290 + 453 = 743. That's a huge number for any batsman by today's standards.
So if he's played 743 innings and total centuries are 98, then
98 / 743 * 100 = 13.19%.
So his total conversion rate for centuries is 13.19% per game to get a century. For a batsman who has opened 330 ODI innings for his country.