Initial Margin is the amount of collateral required to open a position for leverage trading.
To calculate an initial margin, multiply the order value with the initial margin rate. The initial margin rate depends on the leverage used. Assuming you use a 100x leverage in a contract value of 100 dollars; you would only need to invest 1 dollar as your initial margin (1/100).
To check the initial margin rate for your position, and the maximum leverage you can use, you may refer to the risk limit table.
A trader buys 12,000 BTCUSD contracts at 8,000 USD with 50x leverage.