There are probably better ways but this is all I could come up with as a beginner.

package.manifest

{
    propertyEditors:
    [ 
        {
            alias: "Aneto.Dash",
            name: "Aneto Dashboard",
            editor:
            {
                view: "~/App_Plugins/Aneto/DashboardAd.html"
            }
        }
    ],

    javascript:
    [
        "~/App_Plugins/Aneto/Aneto.Ad.controller.js",
        "~/App_Plugins/Aneto/Aneto.Ad.resource.js"
    ]
 }

DashboardAd.html

<link href="/css/dashboard.css" rel="stylesheet" />
<script src="Aneto.Ad.controller.js"></script>

<div ng-controller="Aneto.DashController">

    <div class="DashboardAdvertenties">
        <h2><img src="/images/icons/Pages-icon.png" width="35" height="35" alt="" /> Advertenties</h2>
        <ul>
            <li>Totaal Aantal Advertenties: <span class="DashboardNr"> {{ TotaalAds }} </span></li>
            <li>Aantal Open Advertenties: <span class="DashboardNr"> {{ TotaalOpenAds }} </span></li>
            <li>Aantal Gesloten Advertenties: <span class="DashboardNr"> {{ TotaalGeslotenAds }} </span></li>
            <li>Aantal Reacties: <span class="DashboardNr"> {{ TotaalReacties }} </span></li>
        </ul>
    </div>

    <div class="DashboardAdvertenties">
        <h2><img src="/images/icons/Icon-user.png" width="25" height="25" alt="" /> Gebruikers</h2>
        <ul>
            <li>Aantal geregistreerde gebruikers: <span class="DashboardNr"> {{ TotaalGebruikers }} </span></li>
        </ul>
    </div>

</div>

Aneto.Ad.controller.js

angular.module("umbraco").controller("Aneto.DashController", function ($scope, notificationsService, dashResource) {

    dashResource.getAdvertisementModel().then(function (response) {
        $scope.TotaalAds = response.data.TotaalAds;
        $scope.TotaalOpenAds = response.data.TotaalOpenAds;
        $scope.TotaalGeslotenAds = response.data.TotaalGeslotenAds;
        $scope.TotaalReacties = response.data.TotaalReacties;
        $scope.TotaalGebruikers = response.data.TotaalGebruikers;

    }, function(response) {
                        notificationsService.error("Error", "Error loading documents");
                        console.log(response.data);
                    });
    }
);

Aneto.Ad.resource.js

angular.module('umbraco.resources').factory('dashResource', function ($q, $http) {
    return {
        getAdvertisementModel: function () {
            return $http.get("backoffice/Aneto/AnetoApi/GetAdvertisementModel");
        }
    };
});

AnetoApiController.cs

using System.Linq;
using umbraco;
using Umbraco.Core.Models;
using Umbraco.Web;
using Umbraco.Web.Editors;
using Umbraco.Web.Mvc;
using Umbraco.Web.WebApi;

namespace Web.Controllers.Api
{
    [PluginController("Aneto")]
    [IsBackOffice]
    public class AnetoApiController : UmbracoAuthorizedJsonController
    {
        private int TotaalOpenAdsTemp;
        private int TotaalGeslotenAdsTemp;

        public AdvertismentTotalViewModel GetAdvertisementModel()
        {
            IPublishedContent homePage = Umbraco.TypedContentAtRoot().First();
            var advertentieOverview = homePage.Descendants("Advertenties");
            var advertentieItems = advertentieOverview.DescendantsOrSelf("AdvertentieItem");

            var alleAdvertentieItems = uQuery.GetDocument(1068).GetChildDocuments();

            foreach (var item in advertentieItems)
            {
                var test = item.Properties.FirstOrDefault(p => p.PropertyTypeAlias == "status").Value.ToString();
                if (item.Properties.FirstOrDefault(p => p.PropertyTypeAlias == "status").Value.ToString() == "Open")
                {
                    TotaalOpenAdsTemp = TotaalOpenAdsTemp + 1;
                }
            }

            return new AdvertismentTotalViewModel()
            {
                TotaalAds = alleAdvertentieItems.Count(),
                TotaalOpenAds = TotaalOpenAdsTemp,
                TotaalGeslotenAds = alleAdvertentieItems.Count() - TotaalOpenAdsTemp,
                TotaalReacties = 0,
                TotaalGebruikers = umbraco.cms.businesslogic.member.Member.GetAll.Count()
            };
        }
}

    public class AdvertismentTotalViewModel
    {
        public int TotaalAds { get; set; }
        public int TotaalOpenAds { get; set; }
        public int TotaalGeslotenAds { get; set; }
        public int TotaalReacties { get; set; }

        public int TotaalGebruikers { get; set; }
    }
}