Correct way to Get specific posts from a topic (Discourse API)

The API to get all posts given a topic only returns the first 20 posts. To get remaining posts I would like to use the API to get specific posts for a topic

From the API docs Discourse API Docs

It says to send a request with Request Body schema: application/json

    "post_ids[]": integer

I don’t understand this request body can someone give an example? Is it supposed to be an array? A single integer?

EDIT Also it seems to be a GET request, why is there a Request body?

To see how it’s working, check out Reverse engineer the Discourse API and see how the front end does it.