Cost distribution using IT 0027 seems to be straigtforward. At payroll run the cost is distributed directly based on the percentages indicated in IT 0027. It ignores the position holder percentage. For example if the amount of the wage type is $1000 and the percentages against a cost center 'An' is 30% then the amount of $300 is charged to CC 'An' and the balance is automatically charged to the Master Cost Centre.
However, if you use IT 1018 to distribute cost, at payroll run, the system looks at the position holder (relationship A 008) percentage to determine the actual percentage. For example, if you assume the same distribution of 30% for CC 'An', and the holder percentage is say 50%, the system calculates 30% of 50 i.e. 15% or $ 150 to charge to the cost centre.
I would appreciate if you could give me a logical explanation for this behavious so I can be better prepared to answer questions from users.