Fee calculation method

Perpetual Futures only support trading using USDT, so fees can only be deducted in USDT.
For example: A user places a market order to sell 0.5 BTC for 25,000 USDT in the BTC/USDT perpetual Futures and then sets a limit order to buy 0.4 BTC for 22,000 USDT. The user's fee calculation is as follows:
For instance:
Maker fee rate: 0.06%
Taker fee rate: 0.06%
Fee for selling short: 25,000 * 0.5 * 0.06% = 7.5 USDT
Fee for buying long: 22,000 * 0.4 * 0.06% = 5.28 USDT