On 9 May 2017, the Treasurer directed that the maximum face value of CGS that can be on issue is $600 billion
That is footnote 3 on page 8 of section 7 of Budget Paper 1. Vital information like that should not be hidden in footnotes.
The Australian federal government has authorised itself to borrow six hundred thousand million dollars. On current projections that figure is expected to rise to six hundred and forty nine thousand million dollars.