If you use Google Calendar with OS X Lion or Mountain Lion's Calendar application, you may have noticed your default event alerts showing odd times. For example, when I create a new event, Calendar adds a default alert of 1150 minutes in addition to the Calendar standard default alert of 15 minutes.
The fix to this issue is actually pretty simple:
For the next few steps, you will have to do this for each calendar in your account:
Once you've completed those steps, try creating a new event in Calendar. It should only have the Calendar default alert:
Note: I can only imagine this would work for Google Apps accounts, but I have not tested it.