Online maintenance overlap for database on Exchange 2007

I periodically receive "There is an online maintenance overlap for database..." warning on Exchange 2007 application log.  I have changed my custom schedule for online maintenance but still see it, any idea to fix it?

I have two different database for two different storage groups - Manager.edb and Staff.edb

The schedule of maintenance for Manager.edb is Monday, Wednesday, Friday, 12AM - 4AM
The schedule of maintenance for Staff.edb is Sunday, Tuesday, Thursday, 1AM - 5AM
For Public Folder, the schedule is on Sunday 5pm.

I do not understand why the message still logged in application log.
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Please paste that message here.

KANEWONGAuthor Commented:
sorry, i cleared the log.  Usually, it will show once a week, i will post if I see it again.
Thanks i would wait for that message to appear.

KANEWONGAuthor Commented:

the message is

There is an online maintenance overlap for database "Storage Group Standard\Staff". Please revise the online maintenance schedule.
If it is similar to the following link, be rest assured this wont cause any harm - infact you may want to ignore this just a noise created by Exchange for trivial reasons.

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