Hey there, @VKniss-RDM. 

Thanks for following up with us. I'm here to help sort your average cost out. 

From reviewing over your thread, our champion user, BigRedConsulting, is correct. The average cost is based on your purchase history for the item, calculated from the beginning to date. QuickBooks will compare the new average cost to the average cost used when selling and purchasing more of the item. Therefore, QuickBooks will make an adjustment entry to both the inventory asset and COGS accounts. 

However, it is strange that your average cost is so largely in the negative. With that being said, I recommend resorting the item list to clear any data damage that may be within it. I've included the steps below to do this. 

1. Select List on the upper menu.
2. Choose Item List.
3. Click the Item drop-down arrow at the lower-left, then hit Re-sort List.
   • 
4. Tap Ok.

You can see more details about resorting list in Resort list in QuickBooks Desktop.

If you're continuing to have issues with your average cost, I encourage you to contact our technical support team. They have the tools available to review your account in a secure environment and investigate the issue of its odd behavior.

Please let me know if you have further questions or concerns. You can reach out to the Community at any time. Take care and have a great day ahead!