Understanding Search Query's `facet_by` Implementation

Hi All, When i am making search query with facet_by then whatever facet_counts i am getting is based on per_page ? how i can get whole facets count for the search query. and if my response for search is like this

    "facet_counts": [
        {
            "counts": [
                {
                    "count": 8,
                    "highlighted": "eCommerce",
                    "value": "eCommerce"
                },
                {
                    "count": 2,
                    "highlighted": "Logistics and Supply Chain",
                    "value": "Logistics and Supply Chain"
                }
            ],
            "field_name": "industry_category",
            "sampled": false,
            "stats": {
                "total_values": 2
            }
        }
    ],

how i can get all 8 documents for eCommerce facets.............( I tried filter_by also but it is giving me different results. since eCommerce having 8 facets count but if i filter than i am getting more than 8 results .... ) can anyone help me out for this Thank you !

whatever facet_counts i am getting is based on per_page ?

This is not the case.

Facets are always on the full resultset, unrelated to pagination