AP Invoice Approval Workflow (APINV) - header vs line approval

Hello,

We are in the process of implementing AP Invoice Approval Workflow. At present we are looking only at header approval and have configured AME rule and approver groups for header level only. However, workflow appears to be invoking header approval rules for each line of the invoice.

For example, I have an invoice with 3 lines, for this workflow, I see in the log (custom message in fnd_log_messages from dynamic approver group) that AME has been invoked 3 times for a header approver group.How can this be avoided?

Thanks,

Nagesh