diff --git a/content/experiment/ad-versarials.md b/content/experiment/ad-versarials.md
index 45e9a74..2fd836d 100644
--- a/content/experiment/ad-versarials.md
+++ b/content/experiment/ad-versarials.md
@@ -17,7 +17,7 @@ This experiment invites participants to play with machine listening's corporate
 ## Activity 
 
 - Introduction:
-  - Explain main concepts and issues.
+  - Explain main concepts and issues (15 min)
 - Listening:
   - Spend some time with this [playlist](https://www.youtube.com/playlist?list=PL_WhOEp3AgTU2PG1qUDvJhjG316e-Kw4U) of machine listening advertising and browse around for more. (15 min)
 - Discussion: