Ceph » RADOS

Considering the below example:

[root@node101 ~]# ceph df
RAW STORAGE:
    CLASS     SIZE        AVAIL      USED       RAW USED     %RAW USED 
    hdd        82 TiB     27 TiB     55 TiB       55 TiB         66.82 
    nvme       22 TiB     11 TiB     11 TiB       11 TiB         49.03 
    TOTAL     104 TiB     38 TiB     65 TiB       65 TiB         63.07 

POOLS:
    POOL                          ID     STORED      OBJECTS     USED        %USED     MAX AVAIL 
    images                         1      27 TiB       7.31M      53 TiB     75.18       8.8 TiB 
    volumes_nvme                   2     1.2 TiB     447.17k     2.3 TiB     56.95       893 GiB 
    volumes                        3     525 GiB     137.05k     1.0 TiB      5.49       8.8 TiB 
    vms                            5     4.2 TiB       2.67M     8.3 TiB     82.55       893 GiB 
    .rgw.root                     11     4.5 KiB           5     940 KiB         0       8.8 TiB 
    default.rgw.control           12         0 B           8         0 B         0       8.8 TiB 
    default.rgw.meta              13     5.9 KiB          15     1.8 MiB         0       8.8 TiB 
    default.rgw.log               14         0 B         217         0 B         0       8.8 TiB 
    default.rgw.buckets.index     15     7.9 KiB           5     7.9 KiB         0       8.8 TiB 
    default.rgw.buckets.data      16      32 GiB       4.98k      64 GiB      0.35       8.8 TiB 

vms and volumes_nvme pools are built on the nvme storage class.

While the RAW STORAGE reports 11TB available for nvme, the POOLS reports only 893GB MAX AVAIL.
I understood that the POOLS calculation are done via a complex function, but why is the difference so big?