PR05 Cost distribution error

I am doing cost centre assignemnt at the receipt level in PR05. The trip is charged against cost cnetre A.

There are 10 receipts in the trip.

1,2 - charged to cost centre A

3,4 - charged to cost centre B

5,6 - charged to cost centre C

7-10 - explicit cost assignment not defined

When the statement is printed, it displayed Cost Centre C for recipts 7-10.

Ideally it should display Cost centre A for recipts 7-10.

Then I manually assigned the cost centre A to receipts 7-10. Printed report stated displaying correct values for receipts 7-10.

Is this the bug in standard functionality/any SAP note is available? or this is part of standard functionality.