rules of SLA

rules of SLA

Good afternoon.
I ask to help with adjustment SLA in system ServiceDesk.

Level 1 - very quickly, time of reaction for the request- 1 hour, performance time - 4 hours.

Level 2 - average, reaction time - 1 hour, time of performance of 6 hours.

And still a question:
How to me to hold SLA if created the requestdoesn't answer about working capacity of service more than declared time? It turns out, the request will be delayed.