Rules run from top to bottom. Only the first matching rule is applied. Add a rule, set who it matches, and set the target time. Reorder rules when a more specific case should win.
Support hours decide whether that time counts only inside working hours or around the clock.
A trigger can apply an SLA policy, and it can start when an SLA is approaching a breach or has breached.
If the plan does not include editing SLAs, existing rules stay visible and new changes are unavailable until you upgrade.
SLAs
Set first-response, next-response, and resolution targets for conversations and tickets.
Service level agreements are the time targets for customer work. Open Settings → SLAs.
Rules are separate for conversations and tickets.