Error in elevations with the Mapbox Tilequery API

I make my first steps with mapbox with this example: https://docs.mapbox.com/help/tutorials/find-elevations-with-tilequery-api/

I use axios instead of ajax-fetch-api, but this should not be the problem.

You can find my demo under https://astridx.github.io/mapboxexamples/examples/find-elevations-with-tilequery-api.html and my code here:

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8" />
    <title>Display driving directions</title>
    <meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no" />
    <script src="https://api.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.js"></script>
    <link href="https://api.mapbox.com/mapbox-gl-js/v1.12.0/mapbox-gl.css" rel="stylesheet" />
    <script src="https://cdn.jsdelivr.net/npm/axios/dist/axios.min.js"></script>
    <style>
        body {
            margin: 0;
            padding: 0;
        }

        #map {
            position: absolute;
            top: 0;
            bottom: 0;
            width: 100%;
        }


        .eleInfo {
            position: absolute;
            background-color: #fff;
            z-index: 1;
        }
    </style>
</head>

<body>
    <div class="eleInfo">
        <div>Longitude: <span id='lng'></span></div>
        <div>Latitude: <span id='lat'></span></div>
        <div>Elevation: <span id='ele'></span></div>
    </div>
    <div id="map"></div>

    <script>
        var lngDisplay = document.getElementById('lng');
        var latDisplay = document.getElementById('lat');
        var eleDisplay = document.getElementById('ele');

        lngDisplay.textContent = 'Please click on map.';
        latDisplay.textContent = '-';
        eleDisplay.textContent = '-';

        mapboxgl.accessToken = 'pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4M29iazA2Z2gycXA4N2pmbDZmangifQ.-g_vE53SD2WrJ6tFX7QHmA';
        var map = new mapboxgl.Map({
            container: 'map',
            style: 'mapbox://styles/mapbox/streets-v11',
            center: [86.925278, 27.988056],
            zoom: 15
        });

        function getElevation(lng, lat) {
            var query = 'https://api.mapbox.com/v4/mapbox.mapbox-terrain-v2/tilequery/' + lng + ',' + lat + '.json?layers=contour&limit=50&access_token=' + mapboxgl.accessToken;

            axios.get(query)
                .then(function (response) {
                    console.log(response.data.features);
                    var elevations = [];
                    for (i = 0; i < response.data.features.length; i++) {
                        elevations.push(response.data.features[i].properties.ele);
                    }

                    var highestElevation = Math.max(...elevations);
                    eleDisplay.textContent = highestElevation + ' Meter';
                    lngDisplay.textContent = lng.toFixed(4) + '°';
                    latDisplay.textContent = lat.toFixed(4) + '°';
                })
                .catch(function (error) {
                    console.log(error);
                })
                .then(function () {
                    // immer
                });
        }

        map.on('click', function (e) {
            lng = e.lngLat.lng;
            lat = e.lngLat.lat;

            getElevation(e.lngLat.lng, e.lngLat.lat);
        });
    </script>
</body>

</html>

The elevation is correct for my hometown and for many other places. For Mount Everest, I only see values below 6000 meters. That should be over 8000, right? What am I doing wrong?