The Configuration section of Administration consists of two sub-sections, Default options and Global options.
In Default options section, the administrator can define default settings for all new users. Users can override those settings.
Note that the default all-day event hours can be taken from Jira Time Tracking settings.
The long event display means the display for the events that are either equal to all-day events or longer than them. Based on your preferences, you can adjust the display for long events either on a time grid or in the all-day section of a calendar.
By default event minutes is meant the event’s duration in case it is based on a single date-time picker.