Because the stocks bought that day can't be sold, the number of available stocks is 0, and when they can be sold the next day, the number of available stocks is the number of stocks bought.

T+ 1 is a stock trading system, that is, stocks bought on the same day cannot be sold until the next trading day. "T" refers to the transaction registration date, and "T+ 1" refers to the day after the registration date. In China, Shanghai Stock Exchange and Shenzhen Stock Exchange adopt the trading mode of "T+ 1", while China stock market adopts the trading system of "T+ 1". Stocks bought that day will not be sold until the next trading day.