The value of an unit of contract diffs in different exchanges, and even in the same exchange it differs in different markets.
BTCUSDTcontract is valued at 100 USD, and each alt coin contract is valued at 10 USD.
BTC-USDT-SWAPcontract is valued at 0.01 BTC.
BTC-USD-SWAPcontract is valued at 100 USD.
quantity, the number of traded coins/contracts, we can multiply it by
contract_value to get the total traded coins/USDs.