Waiting for External Application Action to finish

Hellos,

I have a peculiar case , I have a python script which runs fine when I run the package manually but fails when It runs via scheduler. The running python script has "wait for application to finish" enabled. 

The question is 
How does ETL come to know if the process of external application has finished ? Do I provide 1 and 0 in my script to denote success/failure ? 

 

It uses API provided by windows. 

Introduction of 1 and 0 in the exit codes seems to have solved the problem right now. 
 

0 return code is a standard code for success anything else is a failure.