I don't think it's past income I think it's for the up and coming. We just started claiming and had to estimate income for the next 3 months. We only get $35ish a fortnight for FTB B & $50ish for FTB A.
We are getting $400 a fortnight for baby bonus but I think this may be incorrect I thought it was $500ish. Baby bonus isn't based on your income. The new parental payment is taxed whereas baby bonus isn't.
Not sure if any of this helps at all