How does the game engine handle the blend in and blend out of animations

Question

I read that some online answers are :

FinalMatrix = BlendOutWeight * OutMatrix + BlendInWeight * InMatrix

The premise of this answer is that the BlendIn time is the same as the BlendOut time. But what should be the calculation formula for the following situations?

1.BlendIn time is longer than BlendOut time

2.BlendOut time is longer than BlendIn time

3.No previous animation when BlendIn

4.No latter animation when in BlendOut

5.When an animation starts BlendOut, there is no next animation, but at a certain point in the BlendOut process, the next animation with BlendIn is switched