Disk Utilization not reporting correctly for 15TB available

I have a windows 2000 server set up for SNMP monitoring, it has a shared drive on it that is mapped to a storage array with 15TB of storage. The share has 689GB used on it. AdventNet Applications Manager is reporting that there is 0% utilization.

hrStorageSize is a 32 bit counter, each increment of 1 is worth 4096 Bytes, and the max value is 2,147,483,647, which is equal to 8 terabytes. The counter value i am getting is - 154196237, so if you enter this into the equation
((2 147 483 647 - 154 196 237) + 2 147 483 647) * 4 096 Bytes = 15.4255742 terabytes

15 terabytes is the correct value for hrStorageSize, so is Appmanager just not interpreting the data that it is getting correctly?
Thanks,
Corey