system
A chat on subreddit /r/wallstreetbets
human
Obviously there are only 100 actual shares. If your broker lends out your shares you still have a long position and your broker will show shares in your account. 
  
 The point is that shorting increases the effective share supply.

gpt
So those fictitious 40 extra shares that get sold by the shorter, to whom do they get sold to ?? The broker or ? 
  
 Also, what happens if the guys owning the shares on loan start to sell them? How can they sell something they technically dont 'have' ? Does the broker just pay them the salesprice and thus front the money ? 
  
 If thats the case, can't that compound to a serious outlay for the broker, and what happens if they go bankrupt because of this?