Trump claims he is reducing national dept $400 million a day
There are two main issues with his claim. The first one is that during his time in office he hasn't had time to do anything about the debt and any changes that have occured have to do with Obama.
"If anything, he is taking credit for something Obama did." -- Laurence Kotlikoff, an economics professor at Boston University.
Second one is that the debt fluctuates by billions of dollars every day. And as such, a change of $12 billion, or roughly 0.002% of the debt has pretty much no meaning at all. Be it him, or be it Obama's doing.
He is correct that the debt grew by $200 billion during the first 30 days in office, but again, this was not Obama's doing, but Bush's, considering Obama took office during one of the biggest financial crisis.
Maya MacGuineas, the president of the Committee for a Responsible Federal Budget, said that "We applaud the president for focusing on the debt as an important metric of success and economic health, but would point out that the improvement this early in his term has to do with normal fluctuations in spending and revenues rather than new policies he has implemented."
If anything, Trump has and is paving the way for a bigger debt.