Notional Value = Mark Price * Position Size
For example, if the current Mark Price of the BTCUSDT perpetual contract is 20,000 USDT, and your Position Size is 5 BTC, then the Notional Value is 20,000 * 5 = 100,000 USDT.
Notional Value
Notional Value = Mark Price x Position Size, e.g. 20,000 USDT mark price x 5 BTC = 100,000 USDT notional. Used as the basis for futures trading fees instead of margin.