how to stop getting exchange emails telling me "your public folder "\xyz\abc" is becoming too large. The current size is 57mb.

I just upgraded to exchange 2013, and now, I'm getting emails from exchange that say the following:

Your public folder "\Media\Aim Reports\Station Summary" is becoming too large. The current size is 57 MB.<o:p></o:p>

Please reduce the size of your public folder by deleting any items you don't need.

<o:p></o:p>

<o:p>How do I stop them from coming? </o:p>

<o:p>I have already tried this command, but it didn't work:</o:p>

Set-PublicFolder -Identity "\Public Folders" -UseDatabaseQuotaDefaults: $False
Is there a place in the ECP I can just disable it?
Thanks, Dan

<o:p></o:p>

Dan