Ok, you first need to set the FOV to the same as in CSGO, which is 58.72 in R6 if you are using 16:9 resolution as in this example. Just fill the calculator out the same way, be sure to select Hdeg Res as FOV Type for R6 and enter 90 as FOV. Then check the output for "Config FOV" for R6. For Sensitivity 1 just enter 1 as this will give you the best accuracy for the multiplier value.
For iron sight use the values from the first calculation, and use 10 for Sensitivity 2 and Monitor Distance 0% as matching method as this will make the scopes and ADS closest to each other:
Change any values here that fits your setup the best