transform.RotateAround Help

I want to transform an object around a pivot point. I used transform.RotateAround and it is working correctly. The problem is I want to adjust this angle in update.

If I used RotateAround in Update it keeps spinning around.

How to I rotate the object around the pivot point by a specific angle?

     void Start () 
     {
     
         transform.RotateAround(pendulumPivot.transform.position, Vector3.forward,   -2.0f);
     }
     
     void Update () 
     {
     
         transform.RotateAround(pendulumPivot.transform.position, Vector3.forward,   -2.0f);
     }