Please help me about "Preview Image Set"

Good Evening, I have a problem…
I don’t know why sometimes the Graphic River shows the whole “Preview Image Set” as in this item:

and in other items not. For example in this case the"Preview Image Set" is cut:

I usually design all my “Preview Image Set” wide 590px. I don’t know how can I do.

Can anyone help me?
Thank You :slight_smile: Daniela