The runtime tool is a bit weird. The editing components I use don't make this editor very easy and it's very hard to work around. Unfortunately, I'm a bit handcuffed with it.

In any case, once you have "created" the new runtime value, it will become an option in the dropdown. So after you create it, you have to still click the runtime editor again to select it. Once it's selected it should save fine.

Hi Travis Sorry, but it don't work for me

Here's a video showing how it works: http://files.tmdb.org/misc/runtime.mp4

Now it's work, sorry something was wrong in my first trys. Merci Travis