Comment 31 for bug 121510

Indeed, documenting takes time and is not simple, but the sentence alone seems clear, as no ones asked for precision: 'It is based on the scheduled transaction', as requested in the exchanges of this ticket.

So if you have planned +1000/month you will have for each future month +1000 and the same for the debits.
The forecast is the sum of scheduled txn debit and credit, as there were already occurred, until the projected month.