Divide Line Items by Contract Duration for ARR Calculation

Is there already a solution for this topic? We are facing the same problem:
Line item has 12 month runtime and yearly payment as a standard.
> When I update this to 24 month duration and upfront payment its not caluclated corretly. (see picture 1). The sum should be 20.000 €
> We need to adjust the amount from 1 to 2 that the values are right. This is consusing for our teams.
> When I update the item to 24 month runtime and yearly payment than its correct. (see picture 2)
There should be a solution where the runtime and ARR are calculated correctly. I could find the data fields to check whether this could be adjusted.

Best,
Alex