or 64% of the net discretionary budget.'
That in itself is deceptive since "discretionary" is not what you or I would consider to be discetionary, but what the government has deemed to be "needed" regardless of the need involved. In truth, all of it has shown to be discretionary in the past when the desire of politicians has deemed it so.
If you look at it from a strict constitutional standpoint, the only "non-discretionary" portion is defense, since that is ennumerated in the constitution while the rest is at the discretion of the government and subsequent laws.