diff --git a/frontend/src/pages/theatres/TheatreDetailPage.tsx b/frontend/src/pages/theatres/TheatreDetailPage.tsx
index 88a69fd..61012c6 100644
--- a/frontend/src/pages/theatres/TheatreDetailPage.tsx
+++ b/frontend/src/pages/theatres/TheatreDetailPage.tsx
@@ -80,11 +80,11 @@ export default (() => {
       return
 
     const targetTime =
-	((new Date).getTime () - (new Date (theatreInfo.postStartedAt)).getTime ()) / 1000
+	((new Date).getTime () - (new Date (theatreInfo.postStartedAt)).getTime ())
 
     const drift = Math.abs (meta.currentTime - targetTime)
 
-    if (drift > 5)
+    if (drift > 5_000)
       embedRef.current?.seek (targetTime)
   }