CRT Table - Cross Year Retro

Can someone explain, how the CRT table works, when cross year retro is performed?

We have some issues and it is inconistent. For some reason, when processing payroll in 2009 and if the employee has a retro in 2008. The Cumulation Type in the CRT Y and K are populated for 2009. However, for some employee's the for the retro portion in 2008, it populates the CRT in 2008 Y cimulation type and 2009 K cumulation. This is happening with multiple wage type(s), but it does this differently for the same wage type on multiple employee's???

The payment occurs for both of these scenarios on the same date in 2009. However, we encounter different issues in CRT with the retro??

Thanks,