The SLA trigger alert should be in line with the business hours you have set-up. Currently when the automatic e-mail is sent for a ticket not answered within the SLA, the e-mail does not take into account the business hours and only look at the calendar hours.
For instance, my business hours are from 8AM till 5PM. If I open a ticket at 8AM and give it an SLA of 6 hours (so fixed before 2PM) and a SLA escalation alert of 4 hours, I will receive an e-mail alert at 6PM (if the ticket is not fixed in time). This does not make sense since nobody is working at that time. The e-mail alert should be sent at 9AM the next day. Thus the SLA alert would be in line with the Business hours.