The journals are explained here, this works on the assumption that your NET wages are getting posted to the profit and loss account.
So in Account Settings >> Advanced Features you’d need to make sure the following is “Off” so that the NET wages are sitting on the P&L code 7003 before the journal is applied.
They should settle at zero yes, whatever you have going into the NET Wages codes gets moved to Gross wages using the journal. If it’s not at zero you must be missing a journal somewhere, also try extending the search range.
I’m not an accountant, so I can only provide general advice, I would therefore recommend you defer to a bookkeeper/accountant for professional advice.