HDD space missing - calculation inside

Hi,

on my Exchange (it`s a 2010 Version, but couldn`t find a category for this) i have the following configuration:

Mailbox 1 is located on a partition with 300GB of HDD size, which has 43GB left (physical)

I run: Get-MailboxDatabase -Status | Select-Object Server,Name,AvailableNewMailboxSpace
-> Result 170,00 GBwhitspace

after this, i run: Get-MailboxDatabase "DB" | Get-MailboxStatistics | %{$_.TotalItemSize.Value.ToMB()} | Measure-Object -sum -average -max -mi
-> Resut, Sum 16 GB Total itemsize

So, alltogether we have 43GB pysical HDD + 170GB Whitespace + 16GB Totalitemsize= 229GB
Total HDD size 300GB - 229GB makes = 70 GB

So, my question is where is this 70GB located or is there something wrong with my calculation?

Best regard

Markus