The GOP frontrunner appears to have mixed up income and revenue.

On two occasions, this writer has spent weeks striving to demystify the Vatican’s finances. Now I’m attempting to solve the riddle of Donald Trump’s income and net worth. Pope Francis, who recently exchanged barbs with Trump over immigration, has bravely promised to open the Vatican’s books. Trump sounds less righteous in claiming that he won’t publicly release his tax returns while he’s being audited by the IRS, but does pledge to eventually make the highly anticipated filings public.

Until then, voters can glean a great deal of information from two sets of documents the Trump campaign has already provided: A balance sheet released in June, when Trump declared his candidacy for President, and a 92-page Personal Financial Disclosure (PFD) form submitted to the Federal Election Commission a month later.

Neither document is as telling as a tax return would be. But when closely read together, you can learn a great deal about Trump’s financial affairs. Here’s the most concerning thing I learned: Trump appears to have overstated his income, by a lot, which could be the reason he has so far tried to avoid releasing his returns.