[Server side] Get value from repeater into higher level

This might be a silly question, but I cannot figure out how to get only the value of the “set value” called product_id, to the higher level.

Using {{repeat3}} outputs this:

{
  "product_id": [
    {
      "product_id": "7065f342-76d3-4776-ab66-28e6e65c40cc"
    }
  ],
  "amount_expected": 1
}

While what I want is this output:

{
  "product_id": "7065f342-76d3-4776-ab66-28e6e65c40cc",
  "amount_expected": 1
}

I have also tried {{repeat3.product_id}} but that produces NULL.