2 things
1) Option URL is a bit tricky sometimes... there are two URLs.. one with symbol code as symbolCode=-10006 and other with symbolCode=-10003. Sometimes when you open the Option chain link in NSE there is a difference in Spot price shown at top right corner and as part of Option chain data... sometimes more than 40 points.. that is when you need to alternate the URL to fetch the correct table where both numbers are same
2) you can also look at using the FII derivative statistic available at
FII derivatives statistic
Basically comparing with previous days data could show surprising insights about what FII's have in mind as they are majority traders in derivatives
shown some past data for your reference