Interpretation of file system size in zfs

Hi,

Below are the output of df and zfs, can anyone advise how to find out the used size of rpool?

output of df -hZ:

# df -hZ
Filesystem             size   used  avail capacity  Mounted on
rpool/ROOT/s10s         40G    29G   8.1G    79%    /
/devices                 0K     0K     0K     0%    /devices
ctfs                     0K     0K     0K     0%    /system/contract
proc                     0K     0K     0K     0%    /proc
mnttab                   0K     0K     0K     0%    /etc/mnttab
swap                    24G   1.8M    24G     1%    /etc/svc/volatile
objfs                    0K     0K     0K     0%    /system/object
sharefs                  0K     0K     0K     0%    /etc/dfs/sharetab
fd                       0K     0K     0K     0%    /dev/fd
rpool/ROOT/s10s/var     20G   2.8G   8.1G    26%    /var
swap                    24G    88K    24G     1%    /tmp