Hey Dragos,
Once you make any change on lower breakpoint it overrides the cascading. so the specific property is overriden and will not get cascading from top.
Once you changed the value of top margin to 18% in Tablet, it will cascade to Mobile and won’t affect Desktop. and if you make any changes to Desktop it won’t cascade to Tablet and Mobile because the Tablet is overriden.
Hope I understand the question and it did help,
Yanay