1. Need to determine the time of fund purchase. If the fund is closed before 3 pm, then the cost price is the net value of the fund closed that day; For transactions after three o'clock in the afternoon, the cost price is the net value of the fund at the close of the next day. Thereby affecting income. 2. It may be caused by fund dividends. 3. Because the subscription fee when buying a fund will also be deducted from the income, it may also lead to negative income.