Non-negitive number button in angular

I am creating a counting app using the ionic framework. I have a positive button with a predefined number (in services.js) and a corresponding negitive number with the same predefined number to subtract that number. This is the template code;

<a class="item list-inset item-thumbnail-left item item-button-right">
                    <img ng-src=" {{ menu.imgsrc1 }} ">
                    <h2>{{ menu.foodItem1 }}</h2>
                    <p>{{ menu.data1 }}</p>
                    <button id="plus" class="button button-icon icon round-button" ng-click="count = count + {{ menu.calories1 }} "> {{ menu.calories1 }} </button>
                    <button id="minus" class="button button-icon icon round-button" ng-click="count = count - {{ menu.calories1 }} "> - </button>
                </a>

This is the services code;

        var menus = [
                {
                    title: 'Breakfast',
                    foodItem1: "Cereal",
                    data1: 'Calories per 250g serving',
                    imgsrc1: "img/almond.jpg",
                    calories1: 17,
                    foodItem2: "Bread",
                    data2: 'Calories per wholegrain slice',
                    imgsrc2: "img/almond.jpg",
                    calories2: 25,
                    foodItem3: "Pastries",
                    data3: 'Calories per piece',
                    imgsrc3: "img/almond.jpg",
                    calories3: 75
                },
                {
                    title: 'Lunch',
                    description: 'Wrap, Sandwich, Soup...',
                    foodItem1: 'Wrap',
                    data1: 'Calories per wholegrain wrap',
                    imgsrc1: "img/almond.jpg",
                    calories1: 567,
                    foodItem2: "Sandwich",
                    data2: 'Calories per brown slice',
                    imgsrc2: "img/almond.jpg",
                    calories2: 567,
                    foodItem3: "Chicken soup",
                    data3: 'Calories per 250ml bowl',
                    imgsrc3: "img/almond.jpg",
                    calories3: 567
                }
      ];

I do not want the negitive numbers to go below zero. My understanding is that I need to use the Math.floor() method to counteract the button from entering the negative zone but how do I write this without compromising what exists already. Do I need another controller?

I try to understand what you are expecting : You don't want that number count = count - {{ menu.calories1 }} to be negative ?

First, I'm never adding data manipulation to HTML. I call a function of my controller that has the data manipulation.

For instance this : 

     <button id="minus" class="button button-icon icon round-button" ng-click="count = count - {{ menu.calories1 }} "> - </button>

will be changed to 

     <button id="minus" class="button button-icon icon round-button" ng-click="removeCal(menu.calories1)"> - </button>

and the creation of removeCal function into your controller

$scope.removeCal = function(val) {
   $scope.count -= val;
}

Then if you want that number to be >= 0 all the time just add a if rule to manage that case

 $scope.removeCal = function(val) {
   $scope.count -= val;
   if($scope.count <0)
      $scope.count = 0;
}