well sure it says that, but shares were posted in error
Imagine one day you wake up and find $500,000 cash in your account that you know shouldn't be there, but you decide it(s a gift from God and go hog wild trading on margin and loose $200K
The next day you get a call, the money is gone and you are short $200K
You just going to say "We'll the money was in the account and you let me trade it, it's your problem"