SLA steps - what happens when re-opened

So what happens when I have a request and SLA of 30 hours. The request is responded to and closed after 20 hours. 5 hours after, the user reopens it (or it gets reopened via email). How much time do I get before the SLA is violated? Is it 5 hours or do I get a full 30 hours?

We are on build 9236 moving to 9238 so if any behavior changed between those versions, please let me know.

Also, as a feature request, it would be more beneficial of the below fields were countdown timers rather than what we have now. or even better, original SLA time AND a countdown times. I know there is a countdown in the grid view. Adding it here would be less confusing.