If you are asking about the money fund, it is very simple. I have answered others before, because the annualized rate of return is nearly seven days, and every day, every ten thousand shares of income is the same day. If the income of that day is higher than that of eight days ago, but lower than that of the previous day, the annualized income of seven days will increase, and the income per ten thousand copies per day will decrease.
If you are asking about a non-monetary fund, it will be easier. The current net value is higher or lower than the previous day, but other indicators are compared with the net value n days ago or for a long time. As long as the net value is low at that time, the net value of that day will also fall, but in the past n days or a certain period of time, the annualized income will rise.