Animation Issue

So I have an animation which an R15 NPC plays at a specific moment, it’s not looped, and I’ve animated the arm (upper arm, lower arm and hand parts) to move in position (a tiny bit) and rotation but I’ve observed that the arm goes to the default position and rotation before and after the animation is played, I don’t understand why.

If you don’t know what the default position and rotation is, refer to your own avatar’s idle/static arm position and rotation. It’s straight and facing downwards.

At the end of the animation, the arm should be at the correct position and rotation I want it to be (according to the animation).

Also, I’ve rotated and positioned the arm the way I wanted it to be before the animation begins, so I don’t understand why this arm is being forced to be in the default position and rotation pre and post animation play.