How does Photon know to which Player a simple script belongs to (related to RaiseEvents)?

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Hello everyone,
I have a question related to RaiseEvents. I was looking at RaiseEvents today and I understand the whole concept. But the only thing, I don't understand is how an "OnEvent()" function is called. I have a simple script, where I receive a RaiseEvent or send a RaiseEvent if I'm the master client. And how does Photon know that this script should receive the RaiseEvent if I send the RaiseEvent just to one specific player through the ActorNumber of a player. How is the script connected to the ActorNumber? Are all GameObjects or scripts connected with the ActorNumber of the player when he connects?
And yes, I have written this line in Awake(), but this doesn't set the ActorNumber: PhotonNetwork.AddCallbackTarget(this);

Thank you already in advance!