This forum is not for exposure, but I'd like to know, why do you want to know?
(I assume you are talking about the Jimmy Fallon performance)
The method he is using in this effect is pretty complex. I would even argue that he isn't forcing the number. This is advanced magic that most magicians never touch, both because of its complexity and bold nature. The effect that he accomplishes seems to be very simple, a number is named and the card is found at that number, the method is nowhere near that simple.
Some resources to check out.
http://www.penguinmagic.com/p/1378
https://www.vanishingincmagic.com/magic/card-magic/inner-card-trilogy/
http://themagicwarehouse.com/BA5053...THWzdqTqaDvCz1M9SPJb4bQjXumehCiwM_xoCoSHw_wcB
http://themagicwarehouse.com/BK6537...LUaGlUJHMBWrCXreMCHiKxj1IUa7Gxas4mRoCgWzw_wcB
http://themagicwarehouse.com/BA4490...0r7WjSwu5DREEmchYvC5GgBEXtrg1IzaMERoC-jLw_wcB
http://www.penguinmagic.com/p/2514
http://www.penguinmagic.com/p/2980
http://www.ebay.com/itm/like/391669156631?lpid=82&chn=ps&ul_noapp=true
How did he do it? It seems flippant but it is true. He did it through years of study practice trial and error. For more specifics you probably need to understand the principals and techniques involved in the above resources.
If you would like to replicate the trick using a different method I can point you to a few other sources where you can learn an easier less technical version of almost the same trick. There are simplified versions available right here on Theory11.
There might be a few thousand magicians that could replicate what David did here using the same method that he did. Of those magicians there are even fewer that would dare to do it live.