EasilyDo can access all of the calendars connected to your device and it's possible the calendar event exists in multiple calendars and this is why EasilyDo is showing you multiples. If you confirm this is the case, you can select which calendars EasilyDo will give you information for by setting your preferences.
Here are steps to select which calendars EasilyDo can access:
1. From your main feed, tap the icon in the top left corner to get to the Account page
2. Tap 'Preferences'
3. Tap 'Linked Calendars'
4. You'll see all the calendars on your devices with checkboxes next to them
5. Check the boxes for the calendars you would like EasilyDo to give you information and alerts for