iExpenses custom calculate mileage amount

Hi,

I am wondering if someone can help or provide some advice.

I used the AP_WEB_CUST_DFLEX.CustomCalculateAmount extension to calculate the expense line amount based on mileage rates according to our company policy. This seems to work correctly and the expense report is submitted successfully.

However when the expense report is audited by payables the system automatically changes the expense report and updates the claim amount based on the mileage rates within the policy schedule and disregards the calculation in AP_WEB_CUST_DFLEX.CustomCalculateAmount.

Do you know if this is the intended functionality? If so then what's the point of AP_WEB_CUST_DFLEX.CustomCalculateAmount?