--- a/devtools/client/animationinspector/utils.js
+++ b/devtools/client/animationinspector/utils.js
@@ -323,17 +323,18 @@ var TimeScale = {
     let delayX = delay < 0 ? x : this.startTimeToDistance(start);
     // The width of the delay.
     let delayW = this.durationToDistance(Math.abs(delay) / rate);
     // The width of the delay if it is negative, 0 otherwise.
     let negativeDelayW = delay < 0 ? delayW : 0;
     // The width of the endDelay.
     let endDelayW = this.durationToDistance(Math.abs(endDelay) / rate);
     // The start position of the endDelay.
-    let endDelayX = endDelay < 0 ? x + w - endDelayW : x + w;
+    let endDelayX = endDelay < 0 ? x + iterationW - endDelayW
+                                 : x + iterationW;
 
     return {x, w, iterationW, delayX, delayW, negativeDelayW,
             endDelayX, endDelayW};
   },
 
   /**
    * Given an animation, get the background data for .iterations element.
    * This background represents iterationCount and iterationStart.