Trade-in in Liu Fu means that the gold price of that day is reduced by 20, then multiplied by your old weight and then multiplied by the discount. Discount means:

If you are not Liu Fu's gold, you need to check your gold to see its fineness, and then make sure to give you a 7-8 discount. This will convert your old gold price, and then you can choose another piece of jewelry to calculate the price, so you can make up the difference.

If your old gold is Liu Fu, you don't need to multiply it by the discount.

Another point is that the exchange of old gold in Liu Fu is required: if the price of new gold you exchange is 1.3 times that of your old gold, that is, for example, your old gold is10g, you need to exchange it for more than13g. Multiple pieces can be accumulated!