This setting affects how the information is displayed in the Git roll up tab on the Jira issue.
Do not display
This tab is not displayed on the Issue screen for all Jira projects.
Show for all projects
This tab will be displayed on the issue screen for all Jira projects.
Show for selected Jira projects
This tab will only be displayed on selected projects. Define one or more required projects into the textbox.
More on general settings
Git roll up issue tab setting (this page)