Storyline block in Rise - mobile version

Good morning, 
I'm working on a Storyline block to put into my Rise course.

When I'm previewing the laptop version it all looks fine, however if I take a look at the mobile version I notice two black bars on the side. What can I do to make it look better on the mobile version? I have added two screenshots below.

Are there certain dimensions that I should use in my Articulate slide?

Looking forward hearing from you guys:)

Eline