Line for cost element type "Overhead" missing in the Cost Distributions

Please refer to the below screenshot of Cost Information which shows a line of cost element type "Overhead" -

When we see the Cost Distributions, this Overhead line is missing. But if we look at the total amount, the value 21.23PLN includes the Overhead amount. My question is - Why the Overhead line is missing in cost distributions?
Please note that the work order quantity is 100.