Gantt View in the Virto calendar is provided in two views: Task (Days) and Task (Hours). These views allow viewing items grouped by events and see which time exactly planned for them. This view enables to create, delete and move events.
The completion percentage is displayed for events from Tasks list. Please check the data source settings if you want to adjust Tasks view as shown on the screen below. (See Data Source Settings section).
Note: since any field on Integer type can be set as field for completion show, the percentage will not be displayed in case the value of the field is higher than 100%.