Change a Slide Duration on Captivate 2017

I created a CP project from MS PowerPoint adding audio and captions on each of the slides in CP and everything is working perfectly fine. The only issue I have is trying to change the slide duration of few of the slides. I changed the value for the slide duration in the timing tab for the slide but the change of the valued is not accepted. For example, I want to change the slide duration from 46.2 secs to 36 secs and it changes back to 46.2 secs. I did it on a previous project and it worked so I am not sure what I am missing this time!