Can't use all memory for VM

Hi!

I have Microsoft Hyper-V Server 2012 R2 with 16 Gb RAM. I created two VM with 7162 Mb of fixed memory on each. But i can't start both of them. When i tried start second vm i got out of memory error. Why?

PS C:\Users\Administrator> ( Get-WMIObject Win32_OperatingSystem -ComputerName localhost ).FreePhysicalMemory
8184452
PS C:\Users\Administrator> start-vm oldBSD
start-vm : 'oldBSD' could not initialize. (Virtual machine ID 05EA5A45-601F-4CC0-8770-62B97571D8F8)
Not enough memory in the system to start the virtual machine oldBSD with ram
size 7168 megabytes. (Virtual machine ID 05EA5A45-601F-4CC0-8770-62B97571D8F8)
The server ran out of available memory.

Max memory value for second machine is 5740Mb, but with it i have

PS C:\Users\Administrator>  ( Get-WMIObject Win32_OperatingSystem -ComputerName
localhost ).FreePhysicalMemory
2243312