Wrong 'Free Space' when mounting the data directory to an external drive

I have a network share mounted to the /var/www/http/data directory (the rest is stored on local disk for performance reasons).
The network share has 1TB+ of free space left, but I’m running low on the local drive.
Nextcloud only displays the space left on my boot drive, not the network share (where the files are actually saved).


Is there any way to change how the free space is measured? Or is this considered a bug?