Use
When calculating average values, the SAP System uses the average bases of previous periods that are stored for each employee. Starting at the current period, the system performs a relevancy test for the previous period. If the period is relevant, cumulation takes place in a secondary wage type.
In Customizing for Payroll you determine via Time Wage Type Valuation ® Averages Old ®
Create Calculation Rules for Averages the following default values:Taking the current period as the starting point, the number of previous periods that the system must deem relevant and use to calculate averages.
The maximum number of previous periods that the system checks to determine the required number of relevant periods.

The number of relevant periods is two. The maximum number of periods is four. The calculation of the averages takes place in period 8. The system keeps checking previous periods until it has found at least two that are relevant. A maximum of four previous periods are checked, in this example the periods 7, 6, 5 and 4. If the desired number of periods is not found after a maximum check of four previous periods then the calculation of averages is carried out with the fewest number of periods. If the system checks the maximum number of previous periods but fails to find a single relevant period, the average value is 0.