What he's saying is that not everyone will show up, but don't count on as many no shows as Delta is hoping for. If it's oversold by less than 10, I'd say a couple standbys will get on(Depends where you are on the list), but Those NRT flights get oversold by 50 or more sometimes. I'd never count on 50 no shows. So just because the actual available is below zero doesn't mean you won't get on, but don't look at the authorized and think you're golden