The direct answer to your question is that vertical slicing of user stories focuses on deliverable value in each story instead of layered stories that only deliver value when they are all done.
As an example, let's say you have something like this:
As an apartment resident, I want to file a request for maintenance online so that I don't have to wait for ...
If you have already started the sprint - i.e. its an active sprint and you want to see the 'burn-down chart' in hour instead of story points, then you can go to the settings of the board in Jira you can change the burn-down to look at hours instead of story points.