The total government debt = total private sector savings, to the last cent. That is an accounting truth, for every debtor there is a creditor, and the creditor of the public sector as a whole is the private sector.

In reality, when you look at how government debt is actually computed, you will find that government debt is the sum of all the coins and banknotes in circulation, all bank deposits at the central bank, and all treasuries. Basically it's the sum of all the savings denominated in that government's currency. It is purely an accounting illusion, governments could also create money out of nowhere without accounting for it as "debt", but that is the accounting standard we are currently using, mostly an heritage from the gold standard times. I'm not sure what the article accounted for exactly, but if they just did a sum of government debt divided by human population, what the article really means is that there are in circulation about 86k dollars for every human, so the average human has a monetary wealth of 86k (with the median being of course much much lower). We should cheer on that number increasing ,the only bad case is if inflation is higher, so that means in real terms we are on average getting poorer even if we have more dollars per capita.