Yes, the rise and fall of the fund on that day can be judged by the estimated net value of the fund, which is the trend of the fund on that day. Generally, we can judge the fund's rise and fall of the day by looking at the fund's net value estimate at the close (the specific rise and fall is subject to the updated rise and fall), and the fund's net value of the day will not be updated until the second trading day.
The rise and fall of the fund is mainly determined by the investment target. For example, stock funds mainly invest in a basket of stocks, and the rise and fall of the fund is determined by this basket of stocks. When the invested stock goes up, the fund goes up, and when the invested stock goes down, the fund goes down.