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Common : The time unit display on all the reports can be changed from here to either hours/days/default. More details explained here.
Epic Hierarchy / Links Hierarchy:
Time Tracking progress : The time progress % of all the issues of your project can be based on either remaining estimate or original estimate calculation. The formulae to calculate the same is described in detail here.
Story Points: If you wish to include story points for issue types other than Story, select the option “Consider Issues other than Story” to “Yes”. More details explained here.
Common : You can hide/show the columns on Epic Hierarchy through this setting. More details explained here.
Field Names: If the Issue type names have been changed in your Jira instance you need to specify them in the global settings. More details explained here.