Exchanging Coin

#1

Q:->https://online.codingblocks.com/player/16682/content/5052?s=6176

Why answer is 12?
https://drive.google.com/open?id=1VJtYNV2YMgF7eYvkGQIpT5QOmFvpu9Yb

#2

The answer is not 12…it is 13(6+4+3 after exchanging once).