Hello,
Purpose of transaction CO11N is to post actual activity which took place on shop-floor during the execution of operation of the production order to get the actual cost of order and update the variance.
If you want actual = plan/standard in CO11n then don't change the activity values in CO11N.
In confirmation profile OPK0 you have an option to hide or No proposal of Services or Proposal when saving.
Please read F1 help,
You can choose whether the activity proposal is given immediately after entry of the operation to be confirmed, or whether the activities, which have been calculated based on quantity using the confirmed total quantity, are written to the database, when you save your data. Activities that have already been entered are not overwritten.
Best Regards,
R.Brahmankar