You can check the VAR, ELM and ADHOC margins on NSE website. Refer to this page for SBI stock.
SBI’s VAR + ELM + ADHOC margin is 21.6%. So for contract value of 900,000 the applicable margin will be 194,580. On expiry minus 4 days you’ll need 10% of this margin if your Long Option position becomes ITM, so on and so fourth for other days.