Client management system lets you create as many calls/events as you wish. But there is a default duration for an event and a call. For example, the default call duration is 15 minutes and the default event duration is ____. If you create schedule at 5:00 pm and another call at 5:05 pm, you will get this alert. You can either proceed despite the alert or schedule it at a different hour.
You can change this default duration of a call or event at any time.
Click Options > Preferences and change the duration.