When does Post Election edit Fast Formula triggered

Summary

Post Election edit fast formula not triggering

Content

When does the Post Election Edit formula gets triggered. I created a dummy formula and associated the formula to a Plan as post election edit. My assumption was that the post-election edit formula will get triggered immediately when the person selects the plan. But in my case it did not happen. Or does the post-election fire only after the submit button at the end of train stop?

Here is my dummy formula. As you can see I deliberately set SUCCESSFUL flag to ‘N’ to trigger an error condition and was hoping that error message show up. But it did not happen. What am I doing wrong?