diff --git a/src/components/structures/ScrollPanel.js b/src/components/structures/ScrollPanel.js
index 72d5330451..548dd70748 100644
--- a/src/components/structures/ScrollPanel.js
+++ b/src/components/structures/ScrollPanel.js
@@ -765,6 +765,7 @@ export default createReactClass({
     },
 
     _topFromBottom(node) {
+        // current capped height - distance from top = distance from bottom of container to top of tracked element
         return this._itemlist.current.clientHeight - node.offsetTop;
     },