Hi,
Calculation is based on document type.
Case 1: If Document type Not equal to CS,CC and CQ , posting date in selection screen - posting date in Cube. If the difference is between 1 to 30, then it the amount will come in 1-30 days bucket.
Case 2 : If document type is equal to CS,CC and CQ, posting date in selection screen - Net due date in Cube. If the difference is 1- 30 days, then the amount will come in 1-30 days bucket.
Finally 1-30 days bucket will be sum of Case 1 + Case 2.