Large empty space at the bottom of the scroll

Question

I want to have divs (.ra) whose content is:

• a fixed .header
• a .rcs div that contains a few or many .box divs

As one can have many of these .box divs, we need a scroll. The scroll leaves the header fixed.

It seems to be Ok, BUT I have a large empty space at the bottom of the scroll. I don't understand why.

Full code : https://jsfiddle.net/yannn/n4dk2znh/1/

HTML :

<div class="ra">
    <div class="header">
        <div class="ra_name">Martin, John William Harry Slobodan Junior</div>
    </div>
    <div class="rcs" id="ra1_rcs">
        <div class="box">titre</div>
        <div class="box">titre</div>
        ...
        <div class="box">titre</div>
        <div class="box">titre</div>
        <div class="box">titre</div>

    </div>
</div>

CSS :

.ra {
        width: 28%;
        height: 200px;
        float: left;
        border-style: solid;
        margin-left: 1%;
        overflow: auto;
    }

    .header {
        background-color: white;
        color: black;
        height: 50px;
        width: 26%;
        position: absolute;
    }

    .rcs {
        margin-top: 50px;
        margin-bottom: : -50px;
        height: 150px;
    }

    .box {
        width: 60px;
        height: 40px;
        float: left;
        background-color: black;
        border-radius: 3px;
        font-size:80%;
        color: white;
        margin: 1px;
        padding: 1px;
        text-align: left;
        text-overflow: ellipsis;
}

Answer 1

There's text there:

try adding:

.box {
    overflow: hidden;
}