Hi Fatima,
If you run the KKS1 in middle of the month, system will calculate the variance based on the that results and There is no accounting impact at that stage. As per the SAP standard practice, Generally we run the KKS1 at end of the month.
If you exectue the KO88/CO88 transaction, then only system will generate the varaince accounting document and it get update on P&L statement.
Hope this helps you, Please let me know incase of any queries.
Thanks,
Reddy