RAM Usage on Proxmox VM Vs Ram Usage on DSM: How optimize?

[Toots]

Hello, I installed DSM 7.2 on a Proxmox virtual machine, via Arc bootloader.
When I go to my DSM 7.2.1-69057 Update 3, the resource monitor tells me that it is using 5% of the RAM. On the other hand, when I go to the Proxmox virtual machine, it tells me that 10% of the RAM is used. Knowing that I have 16GB of RAM, this seems enormous to me because these figures are constant when the NAS is idle.
Is using the VM normal? Can we optimize this use without restricting DSM? Is it better to install DSM directly on the machine and forget about Proxmox, compared to this RAM usage?

Thanks in advance for your help,

Best regards,