Configure a ‘Business hour’ profile with working hours 09:00 to 18:00 and add an exception for each of the (applicable) days as ‘12:30 to 13:30’. Use this business hour profile in the SLA configuration (take care of the location based business / holiday profiles scenario). The duration configured under the exception rule will not be considered for SLA (i.e., the SLA clock will be off for that period).