That seems about right. Make sure you're putting your sight height @ 2.755", and you should get something pretty close to right, if you're running numbers through a ballistic calculator.
Per procedure, you zero the SDO @ 100m to the top of the dot, making the bottom of the dot your 200m hold, top of the BDC is your 300m hold, etc., but that's with the specified weapons/ammo for that optic....

