Version 3.5.1 of the MoodleBox disk image was just released. This version doesn't offer any functional change compared to MoodleBox 3.5.0.
The version 3.5.0 doesn't automatically expand the default partition to the maximal size fo the SD card. This bug is fixed in version 3.5.1.
If you have version 3.5.0, you can manually expand the default partition by launching
sudo /usr/bin/raspi-config --expand-rootfs in the MoodleBox console or by using the adequate section of the MoodleBox plugin.