When creating a new monitor for "Disk Space" in "System and Server Status" module, changing the "File system to check", selecting "Swap", typing in 10 in "Minimum free space", ensuring "Absolute size" is bulleted, changing drop down to "MB", and saving results the service being down with: "Current status
Only 0 bytes space free".
/dev/md1 swap swap defaults 0 0
# cat /proc/swaps
Filename Type Size Used Priority
/dev/md1 partition 4192888 150796 -1
Webmin is incorrectly reading the swap partition space (a system may also have multiple swap partitions -- both "partitions" and "file" based -- unsure if that is taken into consideration for the "Swap" setting in this module).
In my opinion, this is a worse problem: Changing the minimum free space to "Percentage of total" results in a divide by zero (and fails the webmin interface). Recovery from the Divide by Zero error is only possible if you manually delete the "/etc/webmin/status/services/##########.serv" file (where ####### is the generated numeric file name associated with this Disk Space monitor) since the webmin web interface does not complete the screen write.