The article suggests he started with 10,000 a decade ago. If he did that, then he's impressive.
I see no mention of the $10,000 anywhere in this article. Actually the article does not state how much money he had to trade with so unless you have a source we have no idea how big the account was. According to my speculation he likely had $150,000,000 ($150 million dollars) since that sized account would be able to come close to hitting $15 billion dollars in trading per year. Please note that if you factor in T+3 days to settle funds between trades he likely traded less than 100 times in a 365 day cycle.
This is almost certainly wrong. You don't need $15B to make $15B in total turnover. He could be buying and selling hundreds of times a day, or tens of thousands of times a year, rolling over the same money.
You must factor in the time settlement of funds. Even as a day trader or HFT trader, you are subject to the T+3 day settlement rule . So if he only had a small trading account with $1,000,000 ($1 Million) dollars he would be able to trade that entire $1 million dollars less than 100 times per year with that amount of money due to the T+3 funds settlement rule. So if you do the math, it would not add up to $15 billion in volume.
Actually, we can speculate that he likely had a trading account with $150,000,000 ($150 million dollars) since that sized account would be able to come close to hitting $15 billion dollars in trading so from this number we can safely speculate that his real gain could have been 33%. While impressive for a trader, he definitely did not beat the market since the market went up by 57% so he traded like a mad man trying to play games in the market only to have the market beat him by a whopping additional 24%!