The funny thing is that his promises never made any sense but everyone seemed to eat it up. Out of a ~7 trillion dollar budget, he promised he can cut 2 trillion when the total non defense discretionary spending in the budget = 850b. 850b total. Meaning things you can maybe nibble away at, but definitely not cut even close to all of. The math never mathed.
Which is probably why he started teasing cutting some mandatory spending in a panic, once he realized how shit his numbers are.