Depends how you'e doing quests.
You should have an action id for the chest, then the unique id for the quest, your script should have a function to add the items and set quest value from the script.
2000 is the action id for quest containers. the uid is the quest value, it gets set to 1 when the item is picked up.
If you're using older maps or nostalrius for example, tibia had a specific item that works as a quest item. you need to set the quest id on that then add the item contents. Thse items only have 1 container though, so you'd add a bag and add items in the bag for multiple items as a quest reward.
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