While saving Fragment Bookmarks in Design Studio, what should be given in container parameter ?

When we save Fragment Bookmark in design studio, we need to give a container parameter. My question is that how do we decide this parameter.

I have given the Panel as container for my dashboard , so when I save my bookmark it gets saved. But when I load the same bookmark it does not load. I think the problem is with the container parameter.

Kindly help me to know the use of this parameter.