GridStack Row Issue

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.11.2/lodash.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.2.3/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.11.4/jquery-ui.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/gridstack.js/0.2.5/gridstack.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/gridstack.js/0.2.5/gridstack.css">
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/gridstack.js/0.2.5/gridstack-extra.css">
<div class="container">
    <div class="grid-stack grid-stack-2">
        <div class="grid-stack-item" data-gs-x="0" data-gs-y="0" data-gs-width="1" data-gs-height="1">
            <div class="grid-stack-item-content draghandle">
                Content 1
            </div>
        </div>
        <!-- second -->
        <!--
        <div class="grid-stack-item" data-gs-x="2" data-gs-y="0" data-gs-width="2" data-gs-height="1" data-gs-locked="true">
            <div class="grid-stack-item-content draghandle">
                Content 2
            </div>
        </div>
        -->
        <div class="grid-stack-item" data-gs-x="0" data-gs-y="0" data-gs-width="1" data-gs-height="1">
            <div class="grid-stack-item-content draghandle">
                Content 2
            </div>
        </div>

    </div>
        <br/>
       <div class="grid-stack grid-stack-6">
        <div class="grid-stack-item" data-gs-x="0" data-gs-y="0" data-gs-width="1" data-gs-height="1">
            <div class="grid-stack-item-content draghandle">
                Content 3
            </div>
        </div>
        <div class="grid-stack-item" data-gs-x="0" data-gs-y="0" data-gs-width="1" data-gs-height="1">
            <div class="grid-stack-item-content draghandle">
                Content 4
            </div>
        </div>
    </div>
</div>

CSS

.grid-stack {
    background: silver;
}
.grid-stack-item-content {
    background: yellow;
}
div.container {
    position: absolute;
    left: 0; right: 0; bottom: 0; top: 0;
    border: black dotted 2px;
    margin: 1rem;
}

JavaScript

var options = {
    width: 6,
    handle: '.draghandle',
    float: false,
    acceptWidgets: true
};
$('.grid-stack').gridstack(options);