"As previously mentioned, bid/ask prices are always posted with corresponding bid and ask sizes, which serve as measures of the strength and depth of the bid/ask prices. They tell us about the supply/demand pressures on a stock at a given moment. We can summarize important Bid/Ask size concerns as follows:

• A large bid size indicates a strong demand for the stock.
• A large ask size shows that there’s a large supply of the stock.
• If the bid size is significantly larger than the ask size, then the demand for the stock is larger than the supply of the stock; therefore, the stock price is likely to go up.
• If the ask size is significantly larger than the bid size, then the supply of the stock is larger than the demand for the stock; therefore, the stock price is likely to drop."