How does API response's 'Index in list' option works?

I got a case, where I called an API in a screen and I'm applying dynamic children's loop on text component, and the text of that text component is dynamic which is coming through the response of the API, I choose the option 'index in list' and in my API I'm just having two objects under data filed of type array like this:

response :{
    "code": 200,
    "api_status": 1,
    "message": "Success",
    "data": [
        {},
        {}
    ]
}

in output I'm getting the index of 5 items, I want to know how does it works, through that response how 5 items are getting calculated or how does 'index in list' option works.