Disk space percentage

This is a minor issue, but I'm curious about it.

I have a couple of disk space usage tests on /home (debian linux, ext4).

'df -h' reports:
/dev/nvme1n1p1  5.9G  3.7G  2.2G 64% /home

I get the same percentage output regardless of '-h' (powers of 1024) or 
'-H' (powers of 1000). The gigabyte values differ, the percentage remains 
the same.

Tune2fs reports no reserved blocks on the partition:
tune2fs -l /dev/nvme1n1p1 | grep 'Reserved'
Reserved block count:     0
Reserved GDT blocks:      511
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)

But Monit's status output reports:
space total                  5.8 GB (of which 0.3% is reserved for root user)"

my disk space argument is:

# HOME
check filesystem homefs with path /home
every 5 cycles
if space greater 63 %
then exec /usr/local/bin/pushover
repeat every 5 cycles

The problem is, I will begin getting alerts before it reached 64% - as 
reported by df - example:

host [xxxxx] homefs - space usage 63.0% matches
resource limit [space usage > 63.0%

As I said, minor - very minor - issue, though it is curious that Monit 
thinks there are reserved blocks on a partition with none. It'd just be 
great if there were a way to conform the output to match df's output.

-- 
Paul Theodoropoulos
www.anastrophe.com