Was looking into how the business hours works in SLA.
For this we a created new SLA record on CreatedOn field and which will update one of the fields on warning after one minute and some other field on failure after waiting for 5 minute.
And Applicable When -> when the Title field of Case contains “mm” text in it.
Following was the schedule
We created case record that satisfies the above condition at 3:28 P.M.
It updated one field on warning after one minute and then on 3:30 it went into wait condition and then resumed at 3:40 and showed failure at 3:43 as expected (i.e. total 5 minutes).
So it did consider the Break specified and on resuming ran for the remaining 3 minutes.
Hope it helps..