You only can set a fixed duration, then comment this video recently. We will optimize the duration function, and change it to be a range in the next update, please wait for the news.
Here is the sample task:
/editor/attached/file/20190220/20190220153403_0511.zip
Here is a little issue for the view video and comment function, i already informed the programmer to check and fix it soon, please wait for the update.