Every short seller anticipates a declining stock market.
A profit is made if the stock is bought back at a lower price than when it was sold short. Odd lot transactions are made by small investors who can not afford to buy or sell short a round lot of 100 shares of a stock. In the old days this indicator reflected the shorting activity of the smallest of the small guys who where usually dead wrong at bottoms and tops. Since the introduction of options, however, it has lost a lot of its value. Many traders also sell in 99-share lots in fast markets for a better execution of their orders.