question about short rule on DAS

[zyxjl143 0]

When I read the rules of "short " on DAS, it says 

 DOWNTICK - Must short at least $.01 above the bid. If the spread is .01, you may short at the ASK. You can enter a short sell on a listed security (stock symbols with three or fewer letters, example: GE, LU, QQQ, COM, etc.) on a downtick; however, the specialist on the trading floor won't actually place the order until the stock has an up tick. 

That is really confusing, when will they execute the short order ? Can't I short the four letter stocks such as TVIX?

Does that mean if the stock is selling off, I can't shot the stock at bid ?