Thank you Mark and Daniel, settings found!
The problem I guess was in the language since in italian it has been translated with the english meaning of "Interruption width", which, in the context of responsiveness, doesn't mean much...
By the way, problem solved!
@Daniel: no, actually I don't want to use the same width as the object size since it is a map with pretty large margins and I want it to stay the same size until I have space to crop. This was the origin of the problem actually, I feared that Hype used the layout size as a breakpoint and not a different value. Fortunately, at Tumult they thought it right