SQL Server total memory less than target memory, lot of extra memory unallocated
This is normal.  

Max server memory means that your server cannot use more than that amount, not that it must use that amount.  Min server memory doesn't mean it must use that amount, either;  it means that once the server uses that much it doesn't surrender memory to below that amount.  Basically, SQL Server uses the amount of memory it needs until it reaches the upper limit you set, and if it stops using it it might surrender part of it back unless you've set a min memory.  (However, in my experience, it's pretty memory-greedy.)

In short:  This means that you're currently not using 6GB of memory on your SQL Server.