How to specify maximum duration in an incoming transformation


I'm adding an incoming transformation in my unsigned upload preset to set a maximum duration of 9 sec per video whenever a video is uploaded client-side. So, if user uploads a video>9 sec, the video duration would be cut to 9 sec.

I'm using the conditional field in the incoming transformation section to set this up:

However, once this condition is added I get a 400 error when a video is uploaded (if I remove this condition everything works fine)

How could I specify this transformation correctly?