system
A chat on subreddit /r/wallstreetbets
human
It's because he doesn't own the shares yet.  Using your example, he would be buying the shares at their current price ($240) and selling them at $210.  That's a worthless contract.   
  
 The extra risk comes from the fact that you can put $60,000 down and have it expire completely worthless if the underlying stock moves the wrong way.

gpt
Is this also known as shorting?