Hello Dennis@254  in additon to that please check the following:

Adjusting Cost Only:
I/C Adjustments Screen: Navigate to Inventory Control > I/C Transactions > Adjustments. 
Adjustment Type: Select "Cost Increase," "Cost Decrease," "Both Increase," or "Both Decrease" as needed. 
Cost Adjustment: Enter the cost adjustment amount and specify the adjustment/write-off general ledger account. 
Post or Save: Post or save the transaction.

The following posts could be used as a guide for adjusting costs only.

https://www.greytrix.com/blogs/sageaccpacerp/2013/07/30/different-costing-methods-in-sage-300-erp/

https://communityhub.sage.com/us/sage300/f/databases-and-operating-systems/124022/standard-costing

Hello Dennis@254  in additon to that please check the following:

Adjusting Cost Only:
I/C Adjustments Screen: Navigate to Inventory Control > I/C Transactions > Adjustments. 
Adjustment Type: Select "Cost Increase," "Cost Decrease," "Both Increase," or "Both Decrease" as needed. 
Cost Adjustment: Enter the cost adjustment amount and specify the adjustment/write-off general ledger account. 
Post or Save: Post or save the transaction.

The following posts could be used as a guide for adjusting costs only.

https://www.greytrix.com/blogs/sageaccpacerp/2013/07/30/different-costing-methods-in-sage-300-erp/

https://communityhub.sage.com/us/sage300/f/databases-and-operating-systems/124022/standard-costing