That is short volume, usuall normal investor has nothing to do with it. it is one part of procedure MM conduct the trade process. Any thing that is associated with usuall normal investor is SHORT INTEREST. Short interest numbers tells you how much owners feel the price will fall. Any short interest level over 10% of the float is concidered strong negative sentiment. And anything over 20% you can expect shorts to fight rether then cover a new run.
It is understood if the stock has between 10 & 20% short interest when the price rises, shorters are loosing money and as they try to buy to cover, that increases the price. So markets call this a short cover rally.