It's just a generic Black-Scholes tool, it works w/o any market data.
Best would be if you post a complete example with your source of data and/or tools etc.
Take SPY as the obvious example. Mar 18 2022 400 call = $59.70, SPY price = $452.30. $52.30 of intrinsic value, $7.40 of extrinsic value. The extrinsic value is 12.4% of the option price; this is the price of your insurance.
Over 2 months, let's say SPY moves up by $20 to $472.50. The call is now $72.30 ITM. The Jan 21 2022 380 call is the proxy for your 400 call after two months. The 380 call is worth $75.60; $72.30 = intrinsic value, $3.30 = extrinsic value. So in other words, you capture the $20 upside in SPY, and lose $4.10 of the original extrinsic value. You are $4.10 behind a long stock position (though you only spent 13.1% of the cost of buying 100 shares)
Let's now say that SPY falls by $50 over two months. The 400 call is only $2.30 ITM. The Jan 21 2022 450 call is the proxy for your 400 call after two months. It is worth $14.79; $2.30 in intrinsic value, $12.49 of extrinsic value. If you were long stock, you were down $50. If you own the 400 call, you are only down $44.91.
Let's go further and model a real correction; SPY falls $100 over two months. The Jan 21 2022 500 call is the proxy for the 400 call. It is only worth 35 cents, so essentially zero. Your option position loses $59.70-$0.35 = $59.35. If you owned 100 shares of stock, you lost $100.
Obviously, my calculations assume that IV is unchanged, and that's not going to be true in practice. Honestly, IV is pretty low right now, so in the event of a downturn, it's going to rise, and it will provide a little upside "kick" to your long option.
So to summarize:
SPY + $20 => You lose $4.10 of upside relative to owning shares
SPY - $50 => You lose $5.09 less relative to owning shares
SPY - $100 => You lose $40.65 less relative to owning shares
Does this all make sense? Is this the kind of "insurance" that you were looking for from options?
. Technically-correct-but-uninsightful is a stretch goal