diskspace events Exchange 2013 CU2v2 (1006)

Hi,

We recently configured several Exchange 2013 CU2v2 servers, and receive this event constantly :

source : MSExchangeDiagnostics
eventid : 1006

The performance counter '\\servername\LogicalDisk(HarddiskVolume1)\Free Megabytes' sustained a value of '107,00', for the '15' minute(s) interval starting at '7/08/2013 8:11:00'. Additional information: None. Trigger Name:DatabaseDriveSpaceTrigger. Instance:harddiskvolume1

The performance counter '\\servername\LogicalDisk(D:)\Free Megabytes' sustained a value of '9 052,00', for the '15' minute(s) interval starting at '7/08/2013 8:11:00'. Additional information: None. Trigger Name:DatabaseDriveSpaceTrigger. Instance:d:

Actually there's no diskspace problem on these servers, and I don't get where it get this value.

The performance counter '\\servername\LogicalDisk(C:)\Free Megabytes' sustained a value of '7 002,00', for the '15' minute(s) interval starting at '7/08/2013 8:11:00'. Additional information: None. Trigger Name:DatabaseDriveSpaceTrigger. 
Instance:c:

Is there a place where I find the default settings, and lower the tresholds a little?
I don't want to ignore the events in the monitoring, since the counter itself is quite important.
The 2 last ones seem to be correct, but I also don't get where it gets the first one from.