Filtering on Closed When Created equals true is a report change that can show first call resolution. Closed When Created is a field on the Case object that indicates whether the case was closed when it was created, meaning it was resolved on the first call. Filtering on this field will show only the cases that were closed on the first call. Verified References: : https://help.salesforce.com/s/articleView?id=sf.case_fields.htm&type=5 :
https://help.salesforce.com/s/articleView?id=sf.reports_filtering.htm&type=5