Enter bill for received items-

I am trying to enter a bill for received goods, but there is an expenses tab that has amounts attached to it that affects my end total to pay. Expenses tab relates to what I am assuming are COGS, it won't let me delete or change the lines or amounts. Products received are inventory items, have already been received against the purchase order and are showing in inventory. I have tried to change the amount due, but it won't accept as it does not match the final net amount? Have searched items related, and can't see where these COGS are allocated, and whether it is a system thing or if they were loaded incorrectly.