Need Information about Command qm status id -verbose

Hi,
i played around with some qm commands. As i used qm status <id> -verbose i get info with maxmem: and mem: . Ok maxmem is the maximum of memory the kvm can use. So i would suggest mem: is the actual using memory by the kvm. But if i have a look at it. The systeminfo in gnome desktop say less than a half it it in use.

Can you explain it - could not find any information in the net about -verbose...?
thx