Google FIT Sessions in API differes from the ones in app

I am using the Google FIT REST API via PHP SDK in order to query the store, fetch the sessions & dataset data, aggregate them and display for the user. In general it works however with automatically tracked activities I have a lot of discrepancies (including time, steps, distance and calories).

Questions:

1. Where do automatically detected activities come from?
2. How to overcome this and properly query for "autoamtically detected" activities in Google FIT?
3. How do they do that (the aggregate from within the app) ?

Scopes granted:

https://www.googleapis.com/auth/fitness.activity.read
https://www.googleapis.com/auth/fitness.location.read

The data from the google fit App: Activity (running): 14 april, 15:41 - 16:00, steps: 2802, calories: 203, move minutes: 19

Aggregated data given for session by calling the /aggregate endpoint: Params:

[ 
    'startTimeMillis' => '1618358400000',
    'endTimeMillis' => '1618444799000',
    'aggregateBy' => [
        ["dataTypeName" => "com.google.active_minutes"],
        ["dataTypeName" => "com.google.calories.expended"],
        ["dataTypeName" => "com.google.step_count.delta"],
        ["dataTypeName" => "com.google.distance.delta"]
    ]
]

Response:

{
        "id": "...:activemode:running:...",
        "start": "1618408461088",
        "startDate": {
            "date": "2021-04-14 15:54:21.000000",
            "timezone_type": 3,
            "timezone": "Europe\/Warsaw"
        },
        "end": "1618408901980",
        "endDate": {
            "date": "2021-04-14 16:01:41.000000",
            "timezone_type": 3,
            "timezone": "Europe\/Warsaw"
        },
        "name": "bieganie po po\u0142udniu",
        "description": null,
        "sum": {
            "minutes": 7,
            "calories": 380.7721481323242,
            "distance": 3934.6239171028137,
            "steps": 3363
        },
}

Aggregated data fetched from Sessions API (and normalized):

        {
            "activeTimeMillis": null,
            "activityType": 8,
            "description": "",
            "endTimeMillis": "1618408901980", // normalizes to 14 April 2021 16:01:41
            "id": "...:activemode:running:...",
            "modifiedTimeMillis": "1618411492587",
            "name": "bieganie po po\u0142udniu",
            "startTimeMillis": "1618408461088", // normalizes to 14 April 2021 15:54:21
            "application": {
                "detailsUrl": null,
                "name": null,
                "packageName": "com.google.android.apps.fitness",
                "version": null
            }
        },