scroll-animations/css/scroll-animation-initial-offset-ref.html

<!DOCTYPE html>
<style>

#scroller {
  overflow-y: auto;
  height: 200px;
  border: 2px solid green;
  position: relative;
  background: gray;
}

.spacer {
  height: 1000px;
}

#align {
  box-sizing: border-box;
  width: 100%;
  height: 50px;
  background: rgba(0, 0, 200, 0.2);
  color: white;
  position: absolute;
  border: 1px solid white;
  transform: translateY(200px);
  will-change: transform;
}

#marker {
  width: 100%;
  height: 50px;
  background: #640;
  position: absolute;
  top: 350px;
}

</style>
<div id="scroller">
  <div id="align">TOP</div>
  <div class="spacer"></div>
  <div id="marker">BOTTOM</div>
</div>
<script>
  scroller.scrollTo(0, 200);
</script>