On the product page, extra shipping cost is doubling. Im not sure what's going on.

When I add extra shipping cost per item, the extra shipping cost doubles.

I have added in the back end, the ability to have a flat rate shipping cost that doubles per item, but once the quantity reaches 8, then shipping is free. I actually found this feature built into the plug but it was commented out. It does the job well. So i commented it out again, back to normal so to say, and its is still doubling the extra shipping cost per item.

Can anyone possible help out?