User with unlimited quota but in fact limited to 4.9GB


I’ve a Nextcloud (v. 12.0.3) installed on my web server.
Everything is working fine except the quota per user seems to return wrong results.
My nextcloud data directory is located outside of /var/www/html.
In the admin interface I’ve setup unlimited quota but on the desktop app and the web app I’ve a message that I’m using 2.5 GB on 4.9 GB (50.92 %). But my server is full of space

df -h :
Filesystem      Size  Used Avail Use% Mounted on
udev             16G     0   16G   0% /dev
tmpfs           3.2G  9.2M  3.2G   1% /run
/dev/md1         20G   17G  2.5G  87% /
tmpfs            16G  4.0K   16G   1% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs            16G     0   16G   0% /sys/fs/cgroup
/dev/loop1       81M   81M     0 100% /snap/core/2462
/dev/loop0      180M  180M     0 100% /snap/nextcloud/2184
/dev/md0        283M   54M  210M  21% /boot
/dev/md2        3.6T   69M  3.4T   1% /data
tmpfs           3.2G     0  3.2G   0% /run/user/1000

Please could you tell me what is wrong with my installation ?