I knew it from forum discussion and today I read the article of Jameson Lopp.
It is inaccurate information about total supply of Bitcoin at exactly 21M as we see on media. Jameson explained it very detailed and technically in his article.
The number of coins that are circulating in the market wouldn’t be up to the 21 million because there are already lots of coins that are lost and there are even going to be more of them that would still be lost in the market. So as time goes on the number of coins that would be in the market will reduce. With that said, I’d like to add that as the number of the coins in the market is being reduced, there is going to be an increase in the price of the coin to match the level of supply that is available in the market, since when the supply is low, there would be a higher demand.