Note that I am using the gedit editor (version 2.30.3) in Ubuntu 10.04. Perhaps you would have different results if viewing the file in a different editor or different OS, I don't know. I'm just speaking about my own observations.
EDIT: And I just checked the file again, and found two more tabs with different lengths. One was 7 spaces long, and another one was 6 spaces long. Now chew on that one for a minute or two... :p