The calendar does not have a maximum amount of tasks or events that can be added. If you have multiple tasks all due on the same day, the calendar will not cut these off, allowing for visibility of all of your tasks.

For example, the calendar below has 7 items all due on the same day.

To focus on what matters to you, try using the filtering options for the editorial calendar. Also, to reduce tasks that you don’t need to complete, you can  remove completed tasks from the calendar.