There is no clear standard, and you need to add positions according to the actual market and your own investment habits.

If the fund is in a rising market period and the stocks invested are in a strong period, then every decline callback is the time to add positions, and the funds for adding positions are controlled according to their own positions. If the market is in a downturn, but the early investment industry is good, you can choose to buy at a low price, and then decide to add positions.