SVG is expanding past parent

I've been staring at this and can't figure out why the line isn't paying attention to the height of the parent elements. I can't set a height on the event-container, and the other heights I added to the demo are just for sampling. In the end, I need the arrow line to shrink down / expand up to the overall height of the outer block.
What am I missing here??

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-css -->

.content {
  display: flex;
}

.container {
  display: inline-block;
  height: 100px;
}

.event-number {
  margin-right: 32px;
  margin-top: 8px;
  width: 28px;
  text-align: center;
  font-size: 14px;
  font-weight: 700;
  height: 100%;
}

.event-circle {
  height: 28px;
  border-radius: 28px;
  background-color: #aac9ff;
}

p {
  margin: 0;
  padding-top: 4px;
}

.event-container {
  /*height: calc(100% - 36px);*/
}

.event-container .line {
  stroke: #aac9ff;
  stroke-width: 3px;
}

.event-container .box {
  overflow: visible;
}

.event-container .arrow {
  fill: #aac9ff;
}

<!-- language: lang-html -->

<div class="content">
  <journey-counter class="hydrated">
    <div class="container">
      <div class="event-number">
        <div class="event-circle">
          <p>1</p>
        </div>
        <div class="event-container">
          <svg width="100%" height="100%" xmlns="https://www.w3.org/2000/svg">
            <line class="line" x1="50%" y1="0" x2="50%" y2="100%"></line>
            <svg class="box" x="50%" y="100%">
              <path class="arrow" d="M-5 -10 l10 0 l-5 10 l -5 -10  Z"></path>
            </svg>
          </svg>
        </div>
      </div>
    </div>
  </journey-counter>
  <div>
    CONTENT
  </div>
</div>

<!-- end snippet -->

I ended up solving this by using pure CSS & flexbox in place of SVGs.

https://jsfiddle.net/hornetnz/k27waym5/5/

.arrow-down {
  width: 0; 
  height: 0; 
  border-left: 5px solid transparent;
  border-right:5px solid transparent;
  border-top: 10px solid #aac9ff;
  margin-left: 10px;
}