The Initial Margin is the minimum amount of margin required to establish a leveraged position.
Initial Margin = Notional Value / Leverage
For example, if the current Mark Price of the BTCUSDT perpetual contract is 20,000 USDT, and you open a long position of 5 BTC with a leverage of 10x, then the Notional Value is
20,000 * 5 = 100,000 USDT and the Initial Margin is
100,000 / 10 = 10,000 USDT.