Schedules have an impact on the duration specified in an SLA definition.
This impact is reflected in the timings that are taken into consideration while calculating an SLA.
Consider a scenario where you select a duration of one day, which is 24 hours, and a schedule of 9 am to 5 pm, which is 8 hours. The SLA calculation will distribute the 24 hours across three working days of 8 hours each. So a team working on a task associated with this SLA has 3 days to complete the task before the SLA is breached.