Yep, the Offset either adds to or subtracts from the VID to give you your actual core voltage, but it's always before vDroop or vRise. So, it's easiest to find out what your idle voltage is first before switching to Offset mode so that you can find the difference between your idle voltage and the VID so that you have a better chance of ending up with the same voltage once you switch to Offset Mode. So for example, let's say that your idle voltage is 1.328V. This is 0.128V higher than the VID of 1.200V, so your offset would need to be either +0.1250V or +0.1300V. With whatever amount of vDroop or vRise you have, your voltage under load should end up being the same as it was before switching over.