KSS2 refers to actual cost splitting. Using that transaction all the costs which are not being able to attributed to an activity type(s) , will get attributed based on the Plan cost splitting which has happened and posted. Plan cost splitting can be carried out on the basis of Equivalence numbers assigned to respective activity types or Activity type quantity etc., In a single phrase , we can conclude that Actual cost splitting is based on Plan cost splitting.
The primary objective is to transfer activity independent costs to various activity types.
This will have an impact on the cost estimate if you are using Actual Activity price of prev month for valuating internal activities within Product costing. Splitting facilitates allocation / split of the total costs into fixed portion and variable portion.