Nextcloud Docker instance iconsistent drive size

Nextcloud version
Ubuntu 20.04 server Arm64 (Raspberry Pi)
PHP Version 7.4.19

his may be more appropriate asked on the Docker forum so apologies if that is the case but the problem doesn’t exist with other containers so i’ll start by assuming its a Nextcloud problem.

Basically my Nextcloud instance is not reporting the correct disk size for the /data partition and believes it is almost full. In the admin panel it reports a 651.72 GB disk sda1 mapped to /var/www/html/data.

The drive mounted at /dev/sda on my system is a 1TB drive mounted using fstab to ~/DATA then mapped using the docker-compose.yml

When i run lsblk

sda           8:0    0 931.5G  0 disk 
└─sda1        8:1    0 931.5G  0 part /home/ubuntu/DATA

When i run fdisk -l

Disk /dev/sda: 931.53 GiB, 1000204886016 bytes, 1953525168 sectors
Disk model: USB3.0 DISK00   
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 62538339-C588-44F7-BD3A-E757E621D4A7

Device     Start        End    Sectors   Size Type
/dev/sda1   2048 1953523711 1953521664 931.5G Linux filesystem

However running df -h returns

/dev/sda1       687G  652G  431M 100% /home/ubuntu/DATA

I have run fsck and some repairs were made to the drive but the discrepancy still exists

Can anyone help me understand whee this discrepancy in the drive size is occurring, is it to do with the docker container or is there an error in the partition table on the disk and nothing to do with the Nextcloud instance at all.

Any tips appreciated.