Created a new volume of 20Gb, but dh -f shows size as 368M

From the dashboard, I created a new volume of 20Gb.

I followed the mount instructions, and got it mounted. Specifically, I did this (copy pasting here what I copy pasted from the configuration instructions)

# Create a mount point for your volume:
$ mkdir -p /mnt/ek_core_backup

# Mount your volume at the newly-created mount point:
$ mount -o discard,defaults,noatime /dev/disk/by-id/scsi-0DO_Volume_ek-core-backup /mnt/ek_core_backup

# Change fstab so the volume will be mounted after a reboot
$ echo '/dev/disk/by-id/scsi-0DO_Volume_ek-core-backup /mnt/ek_core_backup ext4 defaults,nofail,discard 0 0' | sudo tee -a /etc/fstab

Then I rebooted my droplet. Volumes dashboard indicates it’s attached to the droplet, and I can access it via cd /mnt/ek_core_backup on the terminal.

However, when I tried copying files to it, it complained of size being full for the new mounted point.

Running dh -f thus revealed the /dev/sda mounted on /mnt/ek_core_backup is just showing 368M as max size. Obviously that’s not the expected size.

Am I missing a step?