How to run Reverse Journals (GLPREV) program

If we have a journal created with a non-reversing category and we want to reverse it.  Then we can only reverse it from the Enter Journals form and manually clicking the reverse journals button.  When we do that, it asks for what period to reverse the journal into.  But when I look at the parameters it only shows two parameters being passed into concurrent manager.  These parameters are accesss_set_id and je_header_id.  Question is, how does GLPREV know what period to reverse this journal into if it doesn't get passed in as parameter?

Please reply as early as possible.