Responsive Grid Breakpoints

I’m trying to create a two-column layout for tablets, where the left column should take up “size=‘4’” on large displays (landscape) and “size=‘5’” on medium-and-smaller displays (portrait mode).

I’ve tried following the Ionic v4 documentation, and this “solved” question here on the forum, but can’t get it to work. Unless I use the “size=…” code, the two columns default back to each taking up 50% of the width.

Solved: the documentation is very unclear about how one should actually use “size-sm=’…’” instead of size-sm-#.