RE: GGP - Market26 Oct 2018 17:41
Answer to Q: At the time mentioned, the broker had no stock to sell except for 5,000 [HL]. One assumes that he did not want to raise the price to sell to attract sells. So, the broker has to wait until someone is prepared to sell. If he can get a sell, then one can buy again perhaps more than 5,000 depending on how much was bought. If no one sold for ages, the broker may been forced to raise the selling price to attract the seller.
This is for live dummy quote online.
However, if one wanted to buy, it would probably be NT [Negotiated Trade] either by telephoning but the commission charged may be different or one can place a limit buy or fill and kill. In fill & kill, the broker will try only once and if he cannot get the price, the fill & kill will not be tried again.
So, one can see via trying dummy live buy or sell and the various amount at normal mkt size [NMS] or below or above.
It helps to see if the broker will want to take the sells and how many.
One does not do this all day but at least one can get an idea of what is being quoted etc.