App Calculation Method
A project administrator or a Jira administrator can set the rules of Epic Time calculations per project.
Navigate to Project → Apps → EpicTime and select the rule that will be applied to all epics within this project.
Only a project of Epic matters for the type of calculation. For instance, if you include an issue from a project with the "distributive" rule in an Epic from a project with the "cumulative" rule, the cumulative rule will be applied.