We can explain with math types that the total number of bitcoin t can be mined in total are only 21 millions. 

We can use some math calculations.

Lets start

• A 50-bitcoin reward for each mined block;
• This reward is cut in half every 210000 blocks;
• The indivisible minimum Bitcoin unit is 0.00000001 Bitcoin (which corresponds to 1 Satoshi).

By calculating that 10 minute average time to mine a block, the total will be 21 million as shown in the equations below.

Factoring out common terms (50*210,000) we get the following equation.

The later part of the equation adds up to 2 (or very close to 2) tending to infinity. This collapses the equation to;