Rolling Six Months, Rolling Twelve Months, etc. do not add up the previous X months for each month displayed.
SAP SuccessFactors Workforce Analytics
The purpose of the "Rolling" time models in Query Workspace is not to aggregate, it is to allow greater customisation at runtime. If you apply Rolling Six Months and then click the Time option in the Filters section on the left of Query Workspace or Report Designer, you will see more options than if you'd selected Last Six Months. It allows you to choose one of the last six months and see the six months leading up to that, and also has "Next" and "Previous" options.
Rolling period aggregation of the type you may expect is not possible with these time models as they cannot perform the operations at runtime. Instead a variant of the measure must be requested, and implemented by Cloud Consulting in a development cycle between refreshes. Many customers have Voluntary Termination Rate - Rolling Year, for example, and Rolling Year variants of Terminations and Average Headcount to support it.
KBA , LOD-SF-WFA-WRK , Query Workspace , Problem