External hdd: Difference "Get Info" Available space and "About This Mac - Storage OS X El Capitan.

I have seen this thread, and it explains a bit (different reporting units), but there is an additional substantial discrepancy in the free HDD space of an external HD reported:


Get Info : 11.22GB
df -h    : 1.3Gi
About This Mac - Storage : 1.42 GB




So the differences between About This Mac and df -h can be according to the different units - but the Get Info is heavily off? 

Any ideas what is going on there? 

I know for a fact that the df -h and About This Mac are correct as I can not copy anything larger than the 1.4 Gb on the disk.



ADDITIONAL INFO

These are the hidden files and folders - the rest is stuff I put there:

$ ls -la
-rwxr-xr-x   1 rainerkrug  staff       14340 Nov 10 14:51 .DS_Store
drwx------   5 root        staff         170 Nov 10 18:19 .Spotlight-V100
d-wx-wx-wt   2 root        staff          68 Nov 10 17:36 .Trashes
-rwxr-xr-x@  1 rainerkrug  staff         313 Mar 15  2015 .apdisk
drwx------  15 root        staff         510 Nov 10 18:24 .fseventsd


and their disk usage:

$ sudo du -sch .[!.]* *
 16K    .DS_Store
 11M    .Spotlight-V100
  0B    .Trashes
4.0K    .apdisk
 52K    .fseventsd
You could try sudo mdutil -E / on the terminal, to reindex Spotlight.