how to compute Facebook graph api cover offset_y, offset_x?

I can retrieve facebook cover source and offset_y offset_x from graph api for example.

I get this:

"cover": {
    "cover_id": "100806801653671",
    "offset_x": 50,
    "offset_y": 40,
    "source": "https://scontent.fhan5-3.fna.fbcdn.net/v/t1.0-9/s720x720/97094346_100806804987004_4563790029201080320_o.jpg?_nc_cat=106&ccb=2&_nc_sid=dd9801&_nc_ohc=Cws7sa0H9jcAX9tMEk-&_nc_oc=AQlW59rKI6YR_3RhkI5qYZfQYQhuIKfmz4O4cn-UUkLLEQKnmdX7YgZ4HmjBssvgEuM&_nc_ht=scontent.fhan5-3.fna&tp=7&oh=6a4521a8ddd029b1c6f43c8f4da10823&oe=5FC6470B",
    "id": "100806801653671"
}

But, the actual offset_x and left are different, offset_y and top are different.

Please see iamge this: