a strange file

i open the file with a double click ,it always run inside the sandbox for the first time(since it was transfered to my computer).and later for another time if i double click it,it would run outside the sandbox.then i added the file to the unknown file list to make a online lookup of it,the result shows that the file is known to be clean by comodo.so i 'd like to know why the file always run inside the sandbox for the first time even it’s known to be clean by comodo?
here is the file:
https://forums.comodo.com/news-announcements-feedback-cis/submit-applications-here-to-be-whitelisted-2014-t100712.0.html;msg770730#msg770730

Hi sdfsadfdfs,

It depends. It’s usually because the file is being modified over time.