Calculate Delta Rotation in C++?

I am trying to convert my Anim Blueprint to a C++ animinstance and I am stuck trying to figure out how to calculate the delta rotation from my control rotation and actor rotation. I checked the Delta Rotator blueprint node and it says its located in the Kismet Math Library. However when I check the docs at https://docs.unrealengine.com/4.27/en-US/API/Runtime/Engine/Kismet/UKismetMathLibrary/, I do not see that function. The function said that it is pretty much normalized A-B but I am not really sure what that means. Would I have to normalize both the control rotation and actor rotation and then subtract them? I am not strong with 3d math, can anyone point me in the right direction on how to figure this out as well as some good resources to learn about this kind of math?