I recall that $10 Billion figure was a sworn, FEC document. By law, it's suppose to be accurate.
He's very lucky that's not enforceable.
Part of the problem is that the FEC document is designed to determine conflicts of interest, not net worth. You're allowed to show gross revenues from a business, so it's largely irrelevant. It's not designed to keep people from exaggerating
The second part is that Trump is a relentless liar. By his own admission, his net worth isn't his assets minus his liabilities, but just what he wants to say is true.http://www.newsweek.com/how-much-trump-worth-depends-how-he-feels-384720
The third part is that it doesn't matter in the end how rich Trump is, because we're hiring him to run something, and there's no question that running things is not his forte, as his supporters are quickly learning (just kidding, his supporters don't learn any quickly, if at all). Lots of people make tons of money without being qualified for the presidency. Dumb, poor people think all rich people must be pretty much smart about everything, and it's just not true.