How to stop two BPM rules initiated for the same invoice?

Summary:

One rule is to auto approve when we have a 3 way PO Matched on the header or line Invoice and the other rule is for the invoice to go to the buyer on the PO when there are different types of lines on the invoice such as header match lines or manual entry lines and may it be 2-way or 3 way PO match. Can we have these two different rules and only initiate one without using the preapproved flag (DDF1) set to No?

In the BPM spreadsheet, when I set the two rules preapproved flag (DDF1) both to null, these two rules will initiate together. First the invoice goes to auto approve but then also goes to the buyer, so it will need up in the worklist for the buyer instead of being auto approved. Why would it initiate two rules?