As a new btrfs user, I am myself confused with how much space is used, allocated, or free on my system, and from the looks of a rapid web search, it seems many users are similarly confused. This appears to be because it's actually not a trivial question on btrfs file systems and base GNU/Linux tools like du and df can get confused and give erroneous figures on such systems.

However, that last link to the btrfs wiki does provide command line tools to more accurately assess disk usage (see the "new tools" section). At the moment, I believe the disk-space block uses df, or at least the calculation is pretty similar to what df returns. Would it be possible to make the block compatible with other commands such as the btrfs ones, perhaps by adding an option to indicate the file system in the .toml and use adequate commands to calculate used or free space accordingly?